Oligonucleotide analogues

ABSTRACT

Novel oligomers, and synthesis thereof, comprising one or more bi-, tri-, or polycyclic nucleotide analogues are disclosed herein. The nucleoside analogues have a “locked” structure, termed Locked Nucleoside Analogues (LNA). LNA&#39;s exhibit highly desirable and useful properties. LNA&#39;s are capable of forming nucleobase specific duplexes and triplexes with single and double stranded nucleic acids. These complexes exhibit higher thermostability than the corresponding complexes formed with normal nucleic acids. The properties of LNA&#39;s allow for a wide range of uses such as diagnostic agents and therapeutic agents in a mammal suffering from or susceptible to, various diseases.

FIELD OF THE INVENTION

[0001] The present invention relates to the field of bi- and tricyclic nucleoside analogues and to the synthesis of such nucleoside analogues which are useful in the formation of synthetic oligonucleotides capable of forming nucleobase specific duplexes and triplexes with single stranded and double stranded nucleic acids. These complexes exhibit higher thermostability than the corresponding complexes formed with normal nucleic acids. The invention also relates to the field of bi- and tricyclic nucleoside analogues and the synthesis of such nucleosides which may be used as therapeutic drugs and which may be incorporated in oligonucleotides by template dependent nucleic acid polymerases.

BACKGROUND OF THE INVENTION

[0002] Synthetic oligonucleotides are widely used compounds in disparate fields such as molecular biology and DNA-based diagnostics and therapeutics.

[0003] Therapeutics

[0004] In therapeutics, e.g., oligonucleotides have been used successfully to block translation in vivo of specific mRNAs thereby preventing the synthesis of proteins which are undesired or harmful to the cell/organism. This concept of oligonucleotide mediated blocking of translation is known as the “antisense” approach. Mechanistically, the hybridising oligonucleotide is thought to elicit its effect by either creating a physical block to the translation process or by recruiting cellular enzymes that specifically degrades the mRNA part of the duplex (RNAseH).

[0005] More recently, oligoribonucleotides and oligodeoxyribonucleotides and analogues thereof which combine RNAse catalytic activity with the ability to sequence specifically interact with a complementary RNA target (ribozymes) have attracted much interest as antisense probes. Thus far ribozymes have been reported to be effective in cell cultures against both viral targets and oncogenes.

[0006] To completely prevent the synthesis of a given protein by the antisense approach it is necessary to block/destroy all mRNAs that encode that particular protein and in many cases the number of these mRNA are fairly large. Typically, the mRNAs that encode a particular protein are transcribed from a single or a few genes. Hence, by targeting the gene (“antigene” approach) rather than its mRNA products it should be possible to either block production of its cognate protein more efficiently or to achieve a significant reduction in the amount of oligonucleotides necessary to elicit the desired effect. To block transcription, the oligonucleotide must be able to hybridise sequence specifically to double stranded DNA. In 1953 Watson and Crick showed that deoxyribonucleic acid (DNA) is composed of two strands (Nature, 1953, 171, 737) which are held together in a helical configuration by hydrogen bonds formed between opposing complementary nucleobases in the two strands. The four nucleobases, commonly found in DNA are guanine (G), adenine (A), thymine (T) and cytosine (C) of which the G nucleobase pairs with C, and the A nucleobase pairs with T. In RNA the nucleobase thymine is replaced by the nucleobase uracil (U) which similarly to the T nucleobase pairs with A. The chemical groups in the nucleobases that participate in standard duplex formation constitute the Watson-Crick face. In 1959, Hoogsteen showed that the purine nucleobases (G and A) in addition to their Watson-Crick face have a Hoogsteen face that can be recognised from the outside of a duplex, and used to bind pyrimidine oligonucleotides via hydrogen bonding, thereby forming a triple helix structure. Although making the “antigene” approach conceptually feasible the practical usefulness of triple helix forming oligomers is currently limited by several factors including the requirement for homopurine sequence motifs in the target gene and a need for unphysiologically high ionic strength and low pH to stabilise the complex.

[0007] The use of oligonucleotides known as aptamers are also being actively investigated. This promising new class of therapeutic oligonucleotides are selected in vitro to specifically bind to a given target with high affinity, such as for example ligand receptors. Their binding characteristics are likely a reflection of the ability of oligonucleotides to form three dimensional structures held together by intramolecular nucleobase pairing.

[0008] Likewise, nucleosides and nucleoside analogues have proven effective in chemotherapy of numerous viral infections and cancers.

[0009] Also, various types of double-stranded RNAs have been shown to effectively inhibit the growth of several types of cancers.

[0010] Diagnostics

[0011] In molecular biology, oligonucleotides are routinely used for a variety of purposes such as for example (i) as hybridisation probes in the capture, identification and quantification of target nucleic acids (ii) as affinity probes in the purification of target nucleic acids (iii) as primers in sequencing reactions and target amplification processes such as the polymerase chain reaction (PCR) (iv) to clone and mutate nucleic acids and (vi) as building blocks in the assembly of macromolecular structures.

[0012] Diagnostics utilises many of the oligonucleotide based techniques mentioned above in particular those that lend themselves to easy automation and facilitate reproducible results with high sensitivity. The objective in this field is to use oligonucleotide based techniques as a means to, for example (i) tests humans, animals and food for the presence of pathogenic micro-organisms (ii) to test for genetic predisposition to a disease (iii) to identify inherited and acquired genetic disorders, (iv) to link biological deposits to suspects in crime trials and (v) to validate the presence of micro-organisms involved in the production of foods and beverages.

[0013] General Considerations

[0014] To be useful in the extensive range of different applications outlined above, oligonucleotides have to satisfy a large number of different requirements. In antisense therapeutics, for instance, a useful oligonucleotide must be able to penetrate the cell membrane, have good resistance to extra- and intracellular nucleases and preferably have the ability to recruit endogenous enzymes like RNAseH. In DNA-based diagnostics and molecular biology other properties are important such as, eg., the ability of oligonucleotides to act as efficient substrates for a wide range of different enzymes evolved to act on natural nucleic acids, such as e.g. polymerases, kinases, ligases and phosphatases. The fundamental property of oligonucleotides, however, which underlies all uses is their ability to recognise and hybridise sequence specifically to complementary single stranded nucleic acids employing either Watson-Crick hydrogen bonding (A-T and G-C) or other hydrogen bonding schemes such as the Hoogsteen mode. The are two important terms affinity and specificity are commonly used to characterise the hybridisation properties of a given oligonucleotide. Affinity is a measure of the binding strength of the oligonucleotide to its complementary target sequence (expressed as the thermostability (Tm) of the duplex). Each nucleobase pair in the duplex adds to the thermostability and thus affinity increases with increasing size (No. of nucleobases) of the oligonucleotide. Specificity is a measure of the ability of the oligonucleotide to discriminate between a fully complementary and a mismatched target sequence. In other words, specificity is a measure of the loss of affinity associated with mismatched nucleobase pairs in the target. At constant oligonucleotide size the specificity increases with increasing number of mismatches between the oligonucleotide and its targets (i.e. the percentage of mismatches increases). Conversely, specificity decreases when the size of the oligonucleotide is increased at a constant number of mismatches (i.e. the percentage of mismatches decreases). Stated another way, an increase in the affinity of an oligonucleotide occurs at the expense of specificity and vice-versa.

[0015] This property of oligonucleotides creates a number of problems for their practical use. In lengthy diagnostic procedures, for instance, the oligonucleotide needs to have both high affinity to secure adequate sensitivity of the test and high specificity to avoid false positive results. Likewise, an oligonucleotide used as antisense probes needs to have both high affinity for its target mRNA to efficiently impair its translation and high specificity to avoid the unintentional blocking of the expression of other proteins. With enzymatic reactions, like, e.g., PCR amplification, the affinity of the oligonucleotide primer must be high enough for the primer/target duplex to be stable in the temperature range where the enzymes exhibits activity, and specificity needs to be high enough to ensure that only the correct target sequence is amplified.

[0016] Given the shortcomings of natural oligonucleotides, new approaches for enhancing specificity and affinity would be highly useful for DNA-based therapeutics, diagnostics and for molecular biology techniques in general.

[0017] Conformationally Restricted Nucleosides

[0018] It is known that oligonucleotides undergo a conformational transition in the course of hybridising to a target sequence, from the relatively random coil structure of the single stranded state to the ordered structure of the duplex state.

[0019] A number of conformationally restricted oligonucleotides including bicyclic and tricyclic nucleoside analogues (FIGS. 1A and 1B in which B=nucleobase) have been synthesised, incorporated into oligonucleotide and oligonucleotide analogues and tested for their hybridisation and other properties.

[0020] Bicyclo[3.3.0] nucleosides (bcDNA) with an additional C-3′, C-5 ′-ethano-bridge (A and B) have been synthesised with all five nucleobases (G, A, T, C and U) whereas (C) has been synthesised only with T and A nucleobases (M. Tark{umlaut over (op)}y, M. Bolli, B. Schweizer and C. Leumann, Helv. Chim. Acta, 1993, 76, 481; Tarköy and C. Leumann, Angew. Chem., Int. Ed. Engl., 1993, 32, 1432; M. Egli, P. Lubini, M. Dobler and C. Leumann, J. Am. Chem. Soc., 1993, 115, 5855; M. Tarköy, M. Bolli and C. Leumann, Helv. Chim. Acta, 1994, 77, 716; M. Bolli and C. Leumann, Angew. Chem., Int. Ed. Engl., 1995, 34, 694; M. Bolli, P. Lubini and C. Leumann, Helv. Chim. Acta, 1995, 78, 2077; J. C. Litten, C. Epple and C. Leumann, Bioorg. Med. Chem. Lett., 1995, 5, 1231; J. C. Litten and C. Leumann, Helv. Chim. Acta, 1996, 79, 1129; M. Bolli, J. C. Litten, R. Schultz and C. Leumann, Chem. Biol., 1996, 3, 197; M. Bolli, H. U. Trafelet and C. Leumann, Nucleic Acids Res., 1996, 24, 4660). DNA oligonucleotides containing a few, or being entirely composed, of these analogues are in most cases able to form Watson-Crick bonded duplexes with complementary DNA and RNA oligonucleotides. The thermostability of the resulting duplexes, however, is either distinctly lower (C), moderately lower (A) or comparable to (B) the stability of the natural DNA and RNA counterparts. All bcDNA oligomers exhibited a pronounced increase in sensitivity to the ionic strength of the hybridisation media compared to the natural counterparts. The α-bicyclo-DNA (B) is more stable towards the 3′-exonuclease snake venom phosphordiesterase than the P3-bicyclo-DNA (A) which is only moderately more stable than unmodified oligonucleotides.

[0021] Bicarbocyclo[3.1.0]nucleosides with an additional C-1′,C-6′- or C-6′,C-4′-methano-bridge on a cyclopentane ring (D and E, respectively) have been synthesised with all five nucleobases (T, A, G, C and U). Only the T-analogues, however, have been incorporated into oligomers. Incorporation of one or ten monomers D in a mixed poly-pyrimidine DNA oligonucleotide resulted in a substantial decrease in the affinity towards both DNA and RNA oligonucleotides compared to the unmodified reference oligonucleotide. The decrease was more pronounced with ssDNA than with ssRNA. Incorporation of one monomer E in two different poly-pyrimidine DNA oligonucleotides induced modest increases in T_(m)'s of 0.8° C. and 2.1° C. for duplexes towards ssRNA compared with unmodified reference duplexes. When ten T-analogues were incorporated into a 15mer oligonucleotide containing exclusively phosphorothioate internucleoside linkages, the T_(m) against the complementary RNA oligonucleotide was increased approximately 1.3° C. per modification compared to the same unmodified phosphorothioate sequence. Contrary to the control sequence the oligonucleotide containing the bicyclic nucleoside E failed to mediate RNAseH cleavage. The hybridisation properties of oligonucleotides containing the G, A, C and U-analogues of E have not been reported. Also, the chemistry of this analogue does not lend itself to further intensive investigations on completely modified oligonucleotides (K.-H. Altmann, R. Kesselring, E. Francotte and G. Rihs, Tetrahedron Lett., 1994, 35, 2331; K. -H. Altmann, R. Imwinkelried, R. Kesselring and G. Rihs, Tetrahedron Lett., 1994, 35, 7625; V. E. Marquez, M. A. Siddiqui, A. Ezzitouni, P. Russ, J. Wang, R. W. Wagner and M. D. Matteucci, J. Med. Chem., 1996, 39, 3739; A. Ezzitouni and V. E. Marquez, J. Chem. Soc., Perkin Trans. 1, 1997, 1073).

[0022] A bicyclo[3.3.0] nucleoside containing an additional C-2′,C-3′-dioxalane ring has been synthesised as a dimer with an unmodified nucleoside where the additional ring is part of the internucleoside linkage replacing a natural phosphordiester linkage (F). This analogue was only synthesised as either thymine-thymine or thymine-5-methylcytosine blocks. A 15-mer polypyrimidine sequence containing seven of these dimeric blocks and having alternating phosphordiester- and riboacetal-linkages, exhibited a substantially decreased Tm against complementary ssRNA compared to a control sequence with exclusively natural phosphordiester internucleoside linkages (R. J. Jones, S. Swaminathan, J. F. Millagan, S. Wadwani, B. S. Froehler and M. Matteucci, J. Am. Chem. Soc., 1993, 115, 9816).

[0023] The two dimers (G and H) with additional C-2′,C-3′-dioxane rings forming bicyclic[4.3.0]-systems in acetal-type internucleoside linkages have been synthesised as T-T dimers and incorporated once in the middle of 12mer polypyrimidine oligonucleotides. Oligonucleotides containing either G or H both formed significantly less stable duplexes with complementary ssRNA and ssDNA compared with the unmodified control oligonucleotide (J. Wang and M. D. Matteucci, Bioorg. Med. Chem. Lett., 1997, 7, 229).

[0024] Dimers containing a bicyclo[3.1.0]nucleoside with a C-2′,C-3′-methano bridge as part of amide- and sulfonamide-type (I and J) internucleoside linkages have been synthesised and incorporated into oligonucleotides. Oligonucleotides containing one ore more of these analogues showed a significant reduction in T_(m) compared to unmodified natural oligonucleotide references (C. G. Yannopoulus, W. Q. Zhou, P. Nower, D. Peoch, Y. S. Sanghvi and G. Just, Synlett, 1997, 378).

[0025] A trimer with formacetal internucleoside linkages and a bicyclo[3.3.0]glucose-derived nucleoside analogue in the middle (K) has been synthesised and connected to the 3′-end of an oligonucleotide. The Tm against complementary ssRNA was decreased by 4° C., compared to a control sequence, and by 1.5° C. compared to a sequence containing two 2′,5′-formacetal linkages in the 3′-end (C. G. Yannopoulus, W. Q. Zhou, P. Nower, D. Peoch, Y. S. Sanghvi and G. Just, Synlett, 1997, 378).

[0026] Very recently oligomers composed of tricyclic nucleoside-analogues (L) have been reported to show increased duplex stability compared to natural DNA (R. Steffens and C. Leumann (Poster SB-B4), Chimia, 1997, 51, 436).

[0027] An attempt to make the bicyclic uridine nucleoside analogue Q planned to contain an additional O-2′,C-4′-five-membered ring, starting from 4′-C-hydroxymethyl nucleoside P, failed (K. D. Nielsen, Specialerapport (Odense University, Denmark), 1995).

[0028] Until now the pursuit of conformationally restricted nucleosides useful in the formation of synthetic oligonucleotides with significantly improved hybridisation characteristics has met with little success. In the majority of cases, oligonucleotides containing these analogues form less stable duplexes with complementary nucleic acids compared to the unmodified oligonucleotides. In other cases, where moderate improvement in duplex stability is observed, this relates only to either a DNA or an RNA target, or it relates to fully but not partly modified oligonucleotides or vice versa. An appraisal of most of the reported analogues are further complicated by the lack of data on analogues with G, A and C nucleobases and lack of data indicating the specificity and mode of hybridisation. In many cases, synthesis of the reported monomer analogues is very complex while in other cases the synthesis of fully modified oligonucleotides is incompatible with the widely used phosphoramidite chemistry standard.

SUMMARY OF THE INVENTION

[0029] In view of the shortcomings of the previously known nucleoside analogues, the present inventors have now provided novel nucleoside analogues (LNAs) and oligonucleotides have included LNA nucleoside analogues therein. The novel LNA nucleoside analogues have been provided with all commonly used nucleobases thereby providing a full set of nucleoside analogues for incorporation in oligonucleotides. As will be apparent from the following, the LNA nucleoside analogues and the LNA modified oligonucleotide provides a wide range of improvements for oligonucleotides used in the fields of diagnostics and therapy. Furthermore, the LNA nucleoside analogues and the LNA modified oligonucleotide also provides completely new perspectives in nucleoside and oligonucleotide based diagnostics and therapy.

[0030] Thus, the present invention relates to oligomers comprising at least one nucleoside analogue (hereinafter termed “LNA”) of the general formula I

[0031] wherein X is selected from —O—, —S—, —N(R^(N)*)—, —C(R⁶R⁶*)—, —O—C(R⁷R⁷′)—, —C(R⁶R⁶*)—O—, —S—C(R⁷R⁷*), —C(R⁶R⁶*)—S—, —N(R^(N)*)—C(R⁷R⁷*)—, —C(R⁶R⁶*)—N(R^(N)*)—, and —C(R⁶R⁶*)—C(R⁷R⁷*)—;

[0032] B is selected from hydrogen, hydroxy, optionally substituted C₁₋₄-alkoxy, optionally substituted C₁₋₄-alkyl, optionally substituted C₁₋₄-acyloxy, nucleobases, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands;

[0033] P designates the radical position for an internucleoside linkage to a succeeding monomer, or a 5′-terminal group, such internucleoside linkage or 5′-terminal group optionally including the substituent R⁵;

[0034] one of the substituents R², R²*, R³, and R^(3*) is a group P* which designates an internucleoside linkage to a preceding monomer, or a 3′-terminal group;

[0035] one or two pairs of non-geminal substituents selected from the present substituents of R¹*, R⁴*, R⁵, R⁵*, R⁶, R⁶*, R⁷, R⁷*, R^(N)*, and the ones of R², R²*, R³, and R^(3*) not designating P* each designates a biradical consisting of 1-8 groups/atoms selected from —C(R^(a)R^(b))═C(R^(a))═C(R^(a))—, —C(R^(a))═N—, —O—, —Si(R^(a))₂—, —S—, —SO₂—, —N(R^(a))—, and >C═Z,

[0036] wherein Z is selected from —O—, —S—, and —N(R^(a))—, and Ra and Rb each is independently selected from hydrogen, optionally substituted C₁₋₂-alkyl, optionally substituted C₂₋₁₂-alkenyl, optionally substituted C₂₋₁₂-alkynyl, hydroxy, C₁₋₁₂-alkoxy, C₂₋₁₂-alkenyloxy, carboxy, C₁₋₁₂-alkoxycarbonyl, C₁₋₁₂-alkylcarbonyl, formyl, aryl, aryloxy-carbonyl, aryloxy, arylcarbonyl, heteroaryl, heteroaryloxy-carbonyl, heteroaryloxy, heteroarylcarbonyl, amino, mono- and di(C₁₋₆-alkyl)amino, carbamoyl, mono- and di(C₁₋₆-alkyl)-amino-carbonyl, amino-C₁₋₆-alkyl-aminocarbonyl, mono- and di(C₁₋₆-alkyl)amino-C₁₋₆-alkyl-aminocarbonyl, C₁ ₆-alkyl-carbonylamino, carbamido, C₁₆-alkanoyloxy, sulphono, C₁₆-alkylsulphonyloxy, nitro, azido, sulphanyl, C₁₈-alkylthio, halogen, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, where aryl and heteroaryl may be optionally substituted, and where two geminal substituents Ra and Rb together may designate optionally substituted methylene (═CH₂), and wherein two non-geminal or geminal substitutents selected from R^(a), R^(b), and any of the substituents R¹*, R², R²*, R³, R³*, R⁴*, R⁵, R⁵*, R⁶ and R⁶*, R⁷, and R⁷ which are present and not involved in P, P* or the biradical(s) together may form an associated biradical selected from biradicals of the same kind as defined before; said pair(s) of non-geminal substituents thereby forming a mono- or bicyclic entity together with (i) the atoms to which said non-geminal substituents are bound and (ii) any intervening atoms; and

[0037] each of the substituents R¹*, R², R²*, R³, R⁴*, R⁵, R⁵*, R⁶ and R⁶*, R⁷, and R⁷* which are present and not involved in P, P* or the biradical(s), is independently selected from hydrogen, optionally substituted C₁₋₁₂-alkyl, optionally substituted C₂₋₁₂-alkenyl, optionally substituted C₂₋₁₂-alkynyl, hydroxy, C₁₋₁₂-alkoxy, C₂₋₁₂-alkenyloxy, carboxy, C₁₋₁₂-alkoxycarbonyl, C₁₋₁₂-alkylcarbonyl, formyl, aryl, aryloxy-carbonyl, aryloxy, arylcarbonyl, heteroaryl, heteroaryloxy-carbonyl, heteroaryloxy, heteroarylcarbonyl, amino, mono- and di(C₁₋₆-alkyl)amino, carbamoyl, mono- and di(C₁₋₆-alkyl)-amino-carbonyl, amino-C₁₋₆-alkyl-aminocarbonyl, mono- and di(C₁₋₆-alkyl)amino-C₁₋₆-alkyl-aminocarbonyl, C₁₋₆-alkyl-carbonylamino, carbamido, C₁₋₆-alkanoyloxy, sulphono, C₁₋₆-alkylsulphonyloxy, nitro, azido, sulphanyl, C₁₋₆-alkylthio, halogen, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, where aryl and heteroaryl may be optionally substituted, and where two geminal substituents together may designate oxo, thioxo, imino, or optionally substituted methylene, or together may form a spiro biradical consisting of a 1-5 carbon atom(s) alkylene chain which is optionally interrupted and/or terminated by one or more heteroatoms/groups selected from —O—, —S—, and —(NR^(N))— where R^(N) is selected from hydrogen and C₁₋₄-alkyl, and where two adjacent (non-geminal) substituents may designate an additional bond resulting in a double bond; and R^(N)*, when present and not involved in a biradical, is selected from hydrogen and C₁₋₄-alkyl;

[0038] and basic salts and acid addition salts thereof;

[0039] with the proviso that,

[0040] (i) R³ and R⁵ do not together designate a biradical selected from —CH₂—CH₂—, —O—CH₂—, when LNA is a bicyclic nucleoside analogue;

[0041] (ii) R³, R⁵, and R⁵* do not together designate a triradical —CH₂—CH(−)—CH₂— when LNA is a tricyclic nucleoside analogue;

[0042] (iii) R¹* and R⁶′ do not together designate a biradical —CH₂— when LNA is a bicyclic nucleoside analogue; and

[0043] (iv) R⁴* and R⁶* do not together designate a biradical —CH₂— when LNA is a bicyclic nucleoside analogue.

[0044] The present invention furthermore relates to nucleoside analogues (hereinafter LNAs) of the general formula II

[0045] wherein the substituent B is selected from nucleobases, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands;

[0046] X is selected from —O—, —S—, —N(R^(N)*)—, and —C(R⁶R⁶*)—;

[0047] one of the substituents R², R²*, R³, and R³* is a group Q*;

[0048] each of Q and Q* is independently selected from hydrogen, azido, halogen, cyano, nitro, hydroxy, Prot-O—, Act-O—, mercapto, Prot-S—, Act-S—, C₁₋₆-alkylthio, amino, Prot-N(R^(H))—, Act-N(R^(H))—, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyl, optionally substituted C₂₋₆-alkynyloxy, monophosphate, diphosphate, triphosphate, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, ligands, carboxy, sulphono, hydroxymethyl, Prot-O≦CH₂—, Act-O—CH₂—, aminomethyl, Prot-N(R^(H))—CH₂—, Act-N(R^(H))—CH₂—, carboxymethyl, sulphonomethyl, where Prot is a protection group for —OH, —SH, and —NH(R^(H)), respectively, Act is an activation group for —OH, —SH, and —NH(R^(H)), respectively, and R^(H) is selected from hydrogen and C₁₋₆-alkyl;

[0049] (i) R²* and R⁴* together designate a biradical selected from —O—, —(CR*R*)_(r+s+1)—, —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—, —O—(CR*R*)_(r+s)—O—, —S—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—S—, —N(R*)—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—N(R*)—, —S—(CR*R*)_(r+s)—S—, —N(R*)—(CR*R*)_(r+s)—N(R*)—, —N(R*)—(CR*R*)_(r+s)—S—, and —S—(CR*R*)_(r+s)—N(R*)—;

[0050] (ii) R² and R³ together designate a biradical selected from —O—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—;

[0051] (iii) R² and R³ together designate a biradical selected from —O—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—;

[0052] (iv) R³ and R⁴* together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—;

[0053] (v) R³ and R⁵ together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; or

[0054] (vi) R¹* and R⁴ together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—;

[0055] (vii) R¹* and R²* together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—;

[0056] wherein each R* is independently selected from hydrogen, halogen, azido, cyano, nitro, hydroxy, mercapto, amino, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and/or two adjacent (non-geminal) R* may together designate a double bond, and each of r and s is 0-3 with the proviso that the sum r+s is 1-4;

[0057] each of the substituents R¹*, R², R²*, R³, R⁴*, R⁵, and R⁵*, which are not involved in Q, Q* or the biradical, is independently selected from hydrogen, optionally substituted C₁₋₁₂-alkyl, optionally substituted C₂₋₁₂-alkenyl, optionally substituted C₂₋₁₂-alkynyl, hydroxy, C₁₋₁₂-alkoxy, C₂₋₁₂-alkenyloxy, carboxy, C₁₋₁₂-alkoxycarbonyl, C₁₋₁₂-alkylcarbonyl, formyl, aryl, aryloxy-carbonyl, aryloxy, arylcarbonyl, heteroaryl, hetero-aryloxy-carbonyl, heteroaryloxy, heteroarylcarbonyl, amino, mono- and di(C₁₋₆-alkyl)amino, carbamoyl, mono- and di(C₁₋₆-alkyl)-amino-carbonyl, amino-C₁₋₆-alkyl-aminocarbonyl, mono- and di(C₁₋₆-alkyl)amino-C₁₋₆-alkyl-aminocarbonyl, C₁₋₆-alkyl-carbonylamino, carbamido, C₁₋₆-alkanoyloxy, sulphono, C₁₋₆-alkylsulphonyloxy, nitro, azido, sulphanyl, C₁₋₆-alkylthio, halogen, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, where aryl and heteroaryl may be optionally substituted, and where two geminal substituents together may designate oxo, thioxo, imino, or optionally substituted methylene, or together may form a spiro biradical consisting of a 1-5 carbon atom(s) alkylene chain which is optionally interrupted and/or terminated by one or more heteroatoms/groups selected from —O—, —S—, and —(NR^(N))— where R^(N) is selected from hydrogen and C₁₋₄-alkyl, and where two adjacent (non-geminal) substituents may designate an additional bond resulting in a double bond; and R^(N)*, when present and not involved in a biradical, is selected from hydrogen and C₁₋₄-alkyl;

[0058] and basic salts and acid addition salts thereof;

[0059] with the first proviso that,

[0060] (i) R³ and R⁵ do not together designate a biradical selected from —CH₂—CH₂—, —O—CH₂—, and —O—Si(^(i)Pr)₂—O—Si(^(i)Pr)₂—O—;

[0061] and with the second proviso that any chemical group (including any nucleobase), which is reactive under the conditions prevailing in oligonucleotide synthesis, is optionally functional group protected.

[0062] The present invention also relates to the use of the nucleoside analogues (LNAs) for the preparation of oligomers, and the use of the oligomers as well as the nucleoside analogues (LNAs) in diagnostics, molecular biology research, and in therapy.

BRIEF DESCRIPTION OF THE DRAWINGS

[0063]FIGS. 1A and 1B illustrate known conformationally restricted nucleotides.

[0064]FIG. 2 illustrates nucleotide/nucleoside analogues of the invention.

[0065]FIG. 3 illustrates the performance of LNA modified oligonucleotides in the sequence specific capture of PCR amplicons.

[0066]FIGS. 4A and 4B illustrate that LNA modified oligonucleotides are able to capture its cognate PCR amplicon by strand invasion.

[0067]FIG. 5 illustrates that LNA modified oligonucleotides, immobilised on a solid surface, function efficiently in the sequence specific capture of a PCR amplicon.

[0068]FIG. 6 illustrates that LNA modified oligonucleotides can act as substrates for T4 polynucleotide kinase.

[0069]FIG. 7 illustrates that LNA modified oligonucleotides can function as primers for nucleic acid polymerases.

[0070]FIG. 8 illustrates that LNA modified oligonucleotides can functions as primers in target amplification processes.

[0071]FIG. 9 illustrates that LNA modified oligonucleotides carrying a 5′ anthraquinone can be covalently immobilised on a solid support by irradiation and that the immobilised oligomer is efficient in the capture of a complementary DNA oligo.

[0072]FIG. 10 illustrates that LNA-thymidine-5′-triphosphate (LNA-TTP) can act as a substrate for terminal deoxynucleotidyl transferase (TdT).

[0073]FIG. 11 illustrates hybridisation and detection on an array with different LNA modified Cy3-labelled 8mers.

[0074]FIGS. 12 and 13 illustrate hybridisation and detection of end mismatches on an array with LNA modified Cy3-labelled 8mers.

[0075]FIG. 14 illustrates blockade by LNA of [D-Ala2]deltorphin-induced antinociception in the warm water tail flick test in conscious rats.

[0076]FIGS. 15A, 15B, and 15C illustrate Hybridization and detection of end mismatches on an array with AT and all LNA modified Cy3-labelled 8mers.

[0077]FIGS. 16 and 17 illustrate that LNA can be delivered to living human MCF-7 breast cancer cells.

[0078]FIGS. 18 and 19 illustrate the use of [α³³P] ddNTP's and ThermoSequenase™ DNA Polymerase to sequence DNA templates containing LNA T monomers.

[0079]FIGS. 20 and 21 illustrate that exonuclease free Klenow fragment DNA polymerase I can incorporate LNA Adenosine, Cytosine, Guanosine and Uridine-5′-triphosphates into a DNA strand.

[0080]FIG. 22 illustrates the ability of terminal deoxynucleotidyl transferase (TdT) to tail LNA modified oligonucleotides.

[0081]FIGS. 23A and 23B illustrate that fully mixed LNA monomers can be used to significantly increase the performance of immobilised biotinylated-DNA oligos in the sequence specific capture of PCR amplicons.

[0082] FIGS. 24 to 41 illustrates possible synthetic routes towards the LNA monomers of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0083] When used herein, the term “LNA” (Locked Nucleoside Analogues) refers to the bi- and tri-cyclic nucleoside analogues of the invention, either incorporated in the oligomer of the invention (general formula I) or as discrete chemical species (general formula II). The term “monomeric LNA” specifically refers to the latter case.

[0084] Oligomers and Nucleoside Analogues

[0085] As mentioned above, the present invention i.a. relates to novel oligomers (oligonucleotides) comprising one or more bi-, tri-, or polycyclic nucleoside analogues (hereinafter termed “LNA”). It has been found that the incorporation of such LNAs in place of, or as a supplement to, e.g., known nucleosides confer interesting and highly useful properties to an oligonucleotide. Bi- and tricyclic, especially bicyclic, LNAs seem especially interesting within the scope of the present invention.

[0086] Each of the possible LNAs incorporated in an oligomer (oligonucleotide) has the general formula I

[0087] wherein X is selected from —O— (the furanose motif), —S—, N(RN*—C(R⁶R⁶*)—, —O—C(R⁷R⁷)—, —C(R⁶R⁶*)—O—, —S—C(R⁷R⁷*)—, —C(R⁶R⁶*)—S—, —N(R^(N)*)—C(R⁷R⁷*)—, —C(R⁶R⁶*)—N(^(N)*)—, and —C(R⁶R⁶*)—C(R⁷R⁷*)—, where R⁶, R⁶*, R⁷, R⁷and R^(N)* are as defined further below. Thus, the LNAs incorporated in the oligomer may comprise an either 5- or 6-membered ring as an essential part of the bi-, tri-, or polycyclic structure. It is believed that 5-membered rings (X=—O—, —S—, N(R^(N)*)—, —C(R⁶R⁶*)—) are especially interesting in that they are able to occupy essentially the same conformations (however locked by the introduction of one or more biradicals (see below)) as the native furanose ring of a naturally occurring nucleoside. Among the possible 5-membered rings, the situations where X designates —O—, —S—, and —N(R^(N)*)— seem especially interesting, and the situation where X is —O— appears to be particularly interesting.

[0088] The substituent B may designate a group which, when the oligomer is complexing with DNA or RNA, is able to interact (e.g. by hydrogen bonding or covalent bonding or electronic interaction) with DNA or RNA, especially nucleobases of DNA or RNA. Alternatively, the substituent B may designate a group which acts as a label or a reporter, or the substituent B may designate a group (e.g. hydrogen) which is expected to have little or no interactions with DNA or RNA. Thus, the substituent B is preferably selected from hydrogen, hydroxy, optionally substituted C₁₋₄-alkoxy, optionally substituted C₁₋₄-alkyl, optionally substituted C₁₋₄-acyloxy, nucleobases, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands.

[0089] In the present context, the terms “nucleobase” covers naturally occurring nucleobases as well as non-naturally occurring nucleobases. It should be clear to the person skilled in the art that various nucleobases which previously have been considered “non-naturally occurring” have subsequently been found in nature. Thus, “nucleobase” includes not only the known purine and pyrimidine heterocycles, but also heterocyclic analogues and tautomers thereof. Illustrative examples of nucleobases are adenine, guanine, thymine, cytosine, uracil, purine, xanthine, diaminopurine, 8-oxo-N⁶-methyladenine, 7-deazaxanthine, 7-deazaguanine, N⁴,N⁴-ethanocytosin, N⁶,N⁶-ethano-2,6-diaminopurine, 5-methylcytosine, 5-(C³-C⁶)-alkynylcytosine, 5-fluorouracil, 5-bromouracil, pseudoisocytosine, 2-hydroxy-5-methyl-4-triazolopyridin, isocytosine, isoguanin, inosine and the “non-naturally occurring” nucleobases described in Benner et al., U.S. Pat. No. 5,432,272. The term “nucleobase” is intended to cover every and all of these examples as well as analogues and tautomers thereof. Especially interesting nucleobases are adenine, guanine, thymine, cytosine, and uracil, which are considered as the naturally occurring nucleobases in relation to therapeutic and diagnostic application in humans.

[0090] When used herein, the term “DNA intercalator” means a group which can intercalate into a DNA or RNA helix, duplex or triplex. Examples of functional parts of DNA intercalators are acridines, anthracene, quinones such as anthraquinone, indole, quinoline, isoquinoline, dihydroquinones, anthracyclines, tetracyclines, methylene blue, anthracyclinone, psoralens, coumarins, ethidium-halides, dynemicin, metal complexes such as 1,10-phenanthroline-copper, tris(4,7-diphenyl-1,10-phenanthroline)ruthenium-cobalt-enediynes such as calcheamicin, porphyrins, distamycin, netropcin, viologen, daunomycin. Especially interesting examples are acridines, quinones such as anthraquinone, methylene blue, psoralens, coumarins, and ethidium-halides.

[0091] In the present context, the term “photochemically active groups” covers compounds which are able to undergo chemical reactions upon irradiation with light. Illustrative examples of functional groups hereof are quinones, especially 6-methyl-1,4-naphtoquinone, anthraquinone, naphtoquinone, and 1,4-dimethyl-anthraquinone, diazirines, aromatic azides, benzophenones, psoralens, diazo compounds, and diazirino compounds.

[0092] In the present context “thermochemically reactive group” is defined as a functional group which is able to undergo thermochemically-induced covalent bond formation with other groups. Illustrative examples of functional parts thermochemically reactive groups are carboxylic acids, carboxylic acid esters such as activated esters, carboxylic acid halides such as acid fluorides, acid chlorides, acid bromide, and acid iodides, carboxylic acid azides, carboxylic acid hydrazides, sulfonic acids, sulfonic acid esters, sulfonic acid halides, semicarbazides, thiosemicarbazides, aldehydes, ketones, primary alkohols, secondary alkohols, tertiary alkohols, phenols, alkyl halides, thiols, disulphides, primary amines, secondary amines, tertiary amines, hydrazines, epoxides, maleimides, and boronic acid derivatives.

[0093] In the present context, the term “chelating group” means a molecule that contains more than one binding site and frequently binds to another molecule, atom or ion through more than one binding site at the same time. Examples of functional parts of chelating groups are iminodiacetic acid, nitrilotriacetic acid, ethylenediamine tetraacetic acid (EDTA), aminophosphonic acid, etc.

[0094] In the present context, the term “reporter group” means a group which is detectable either by itself or as a part of an detection series. Examples of functional parts of reporter groups are biotin, digoxigenin, fluorescent groups (groups which are able to absorb electromagnetic radiation, e.g. light or X-rays, of a certain wavelength, and which subsequently reemits the energy absorbed as radiation of longer wavelength; illustrative examples are dansyl (5-dimethylamino)-1-naphthalenesulfonyl), DOXYL (N-oxyl-4,4-dimethyloxazolidine), PROXYL (N-oxyl-2,2,5,5-tetramethylpyrrolidine), TEMPO (N-oxyl-2,2,6,6-tetramethylpiperidine), dinitrophenyl, acridines, coumarins, Cy3 and Cy5 (trademarks for Biological Detection Systems, Inc.), erytrosine, coumaric acid, umbelliferone, texas red, rhodamine, tetramethyl rhodamine, Rox, 7-nitrobenzo-2-oxa-1-diazole (NBD), pyrene, fluorescein, Europium, Ruthenium, Samarium, and other rare earth metals), radioisotopic labels, chemiluminescence labels (labels that are detectable via the emission of light during a chemical reaction), spin labels (a free radical (e.g. substituted organic nitroxides) or other paramagnetic probes (e.g. Cu²⁺, Mg²⁺) bound to a biological molecule being detectable by the use of electron spin resonance spectroscopy), enzymes (such as peroxidases, alkaline phosphatases, p-galactosidases, and glycose oxidases), antigens, antibodies, haptens (groups which are able to combine with an antibody, but which cannot initiate an immune response by itself, such as peptides and steroid hormones), carrier systems for cell membrane penetration such as: fatty acid residues, steroid moieties (cholesteryl), vitamin A, vitamin D, vitamin E, folic acid peptides for specific receptors, groups for mediating endocytose, epidermal growth factor (EGF), bradykinin, and platelet derived growth factor (PDGF). Especially interesting examples are biotin, fluorescein, Texas Red, rhodamine, dinitrophenyl, digoxigenin, Ruthenium, Europium, Cy5, Cy3, etc.

[0095] In the present context “ligand” means something which binds. Ligands can comprise functional groups such as: aromatic groups (such as benzene, pyridine, naphtalene, anthracene, and phenanthrene), heteroaromatic groups (such as thiophene, furan, tetrahydrofuran, pyridine, dioxane, and pyrimidine), carboxylic acids, carboxylic acid esters, carboxylic acid halides, carboxylic acid azides, carboxylic acid hydrazides, sulfonic acids, sulfonic acid esters, sulfonic acid halides, semicarbazides, thiosemicarbazides, aldehydes, ketones, primary alcohols, secondary alcohols, tertiary alcohols, phenols, alkyl halides, thiols, disulphides, primary amines, secondary amines, tertiary amines, hydrazines, epoxides, maleimides, C₁-C₂₀ alkyl groups optionally interrupted or terminated with one or more heteroatoms such as oxygen atoms, nitrogen atoms, and/or sulphur atoms, optionally containing aromatic or mono/polyunsaturated hydrocarbons, polyoxyethylene such as polyethylene glycol, oligo/polyamides such as poly-p-alanine, polyglycine, polylysine, peptides, oligo/polysaccharides, oligo/polyphosphates, toxins, antibiotics, cell poisons, and steroids, and also “affinity ligands”, i.e. functional groups or biomolecules that have a specific affinity for sites on particular proteins, antibodies, poly- and oligosaccharides, and other biomolecules.

[0096] It will be clear for the person skilled in the art that the above-mentioned specific examples under DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands correspond to the “active/functional” part of the groups in question. For the person skilled in the art it is furthermore clear that DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands are typically represented in the form M—K— where M is the “active/functional” part of the group in question and where K is a spacer through which the “active/functional” part is attached to the 5- or 6-membered ring. Thus, it should be understood that the group B, in the case where B is selected from DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, has the form M-K-, where M is the “active/functional” part of the DNA intercalator, photochemically active group, thermochemically active group, chelating group, reporter group, and ligand, respectively, and where K is an optional spacer comprising 1-50 atoms, preferably 1-30 atoms, in particular 1-15 atoms, between the 5- or 6-membered ring and the “active/functional” part.

[0097] In the present context, the term “spacer” means a thermochemically and photochemically non-active distance-making group and is used to join two or more different moieties of the types defined above. Spacers are selected on the basis of a variety of characteristics including their hydrophobicity , hydrophilicity, molecular flexibility and length (e.g. see Hermanson et. al., “Immobilized Affinity Ligand Techniques”, Academic Press, San Diego, Calif. (1992), p. 137-ff). Generally, the length of the spacers are less than or about 400 Å, in some applications preferably less than 100 Å. The spacer, thus, comprises a chain of carbon atoms optionally interrupted or terminated with one or more heteroatoms, such as oxygen atoms, nitrogen atoms, and/or sulphur atoms. Thus, the spacer K may comprise one or more amide, ester, amino, ether, and/or thioether functionalities, and optionally aromatic or mono/polyunsaturated hydrocarbons, polyoxyethylene such as polyethylene glycol, oligo/polyamides such as poly-p-alanine, polyglycine, polylysine, and peptides in general, oligosaccharides, oligo/polyphosphates. Moreover the spacer may consist of combined units thereof. The length of the spacer may vary, taking into consideration the desired or necessary positioning and spatial orientation of the “active/functional” part of the group in question in relation to the 5- or 6-membered ring. In particularly interesting embodiments, the spacer includes a chemically cleavable group. Examples of such chemically cleavable groups include disulphide groups cleavable under reductive conditions, peptide fragments cleavable by peptidases, etc.

[0098] In one embodiment of the present invention, K designates a single bond so that the “active/functional” part of the group in question is attached directly to the 5- or 6-membered ring.

[0099] In a preferred embodiment, the substituent B in the general formulae I and II is preferably selected from nucleobases, in particular from adenine, guanine, thymine, cytosine and urasil.

[0100] In the oligomers of the present invention (formula I), P designates the radical position for an internucleoside linkage to a succeeding monomer, or a 5′-terminal group. The first possibility applies when the LNA in question is not the 5′-terminal “monomer”, whereas the latter possibility applies when the LNA in question is the 5′-terminal “monomer”. It should be understood (which also will be clear from the definition of internucleoside linkage and 5′-terminal group further below) that such an internucleoside linkage or 5′-terminal group may include the substituent R⁵ (or equally applicable: the substituent R⁵*) thereby forming a double bond to the group P. (5′-Terminal refers to the position corresponding to the 5′ carbon atom of a ribose moiety in a nucleoside.)

[0101] On the other hand, an internucleoside linkage to a preceding monomer or a 3′-terminal group (P*) may originate from the positions defined by one of the substituents R², R², R³, and R³*, preferably from the positions defined by one of the substituents R³ and R³*. Analogously, the first possibility applies where the LNA in question is not the 3*-terminal “monomer”, whereas the latter possibility applies when the LNA in question is the 3′-terminal “monomer”. (3′-Terminal refers to the position corresponding to the 3′ carbon atom of a ribose moiety in a nucleoside.)

[0102] In the present context, the term “monomer” relates to naturally occurring nucleosides, non-naturally occurring nucleosides, PNAs, etc. as well as LNAs. Thus, the term “succeeding monomer” relates to the neighbouring monomer in the 5′-terminal direction and the “preceding monomer” relates to the neighbouring monomer in the 3′-terminal direction. Such succeeding and preceding monomers, seen from the position of an LNA monomer, may be naturally occurring nucleosides or non-naturally occurring nucleosides, or even further LNA monomers.

[0103] Consequently, in the present context (as can be derived from the definitions above), the term “oligomer” means an oligonucleotide modified by the incorporation of one or more LNA(s).

[0104] The crucial part of the present invention is the presence of one or more rings fused to the 5- or 6-membered ring illustrated with the general formula 1. Thus, one or two pairs of non-geminal substituents selected from the present substituents of R¹, R⁴*, R⁵, R⁵*, R⁶, R⁶*, R⁷, R⁷*, R^(N)*, and the ones of R² , R²*, R³, and R³* not designating P each designates a biradical consisting of 1-8 groups/atoms, preferably 1-4 groups/atoms, independently selected from —C(R^(a)R^(b))—, —C(R⁴)═C(R^(a))—, —C(R^(a))═N—, —O—, —Si(R^(a))₂—, —S—, —SO₂—, —N(R^(a))—, and >C═Z. (The term “present” indicates that the existence of some of the substituents, i.e. R⁶, R⁶*, R⁷, R⁷*, R^(N)*, is dependent on whether X includes such substituents.)

[0105] In the groups constituting the biradical(s), Z is selected from —O—, —S—, and —N(R^(a))—, and R^(a) and R^(b) each is independently selected from hydrogen, optionally substituted C₁₋₁₂-alkyl, optionally substituted C₂₋₁₂-alkenyl, optionally substituted C₂₋₁₂-alkynyl, hydroxy, C₁₋₁₂-alkoxy, C₂₋₁₂-alkenyloxy, carboxy, C₁₋₁₂-alkoxycarbonyl, C₁₋₁₂-alkylcarbonyl, formyl, aryl, aryloxy-carbonyl, aryloxy, arylcarbonyl, heteroaryl, heteroaryloxycarbonyl, heteroaryloxy, heteroarylcarbonyl, amino, mono- and di(C₁₋₆-alkyl)amino, carbamoyl, mono- and di(C₁₋₆-alkyl)-amino-carbonyl, amino-C₁₋₆-alkyl-aminocarbonyl, mono- and di(C₁₋₆-alkyl)amino-C₁₋₆-alkyl-aminocarbonyl, C₁₋₆-alkyl-carbonylamino, carbamido, C₁₋₆-alkanoyloxy, sulphono, C₁₋₆-alkylsulphonyloxy, nitro, azido, sulphanyl, C₁₋₆-alkylthio, halogen, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands (where the latter groups may include a spacer as defined for the substituent B), where aryl and heteroaryl may be optionally substituted. Moreover, two geminal substituents R^(a) and R^(b) together may designate optionally substituted methylene (=CH₂ optionally substituted one or two times with substituents as defined as optional substituents for aryl), and two non-geminal or geminal substituents selected from R^(a), R^(b), and any of the substituents R¹*, R², R²*, R³, R³*, R⁴*, R⁵, R⁵*, R⁶ and R⁶*, R⁷, and R⁷* which are present and not involved in P, P* or the biradical(s) may together form an associated biradical selected from biradicals of the same kind as defined before. It will be clear that each of the pair(s) of non-geminal substituents thereby forms a mono- or bicyclic entity together with (i) the atoms to which the non-geminal substituents are bound and (ii) any intervening atoms.

[0106] It is believed that biradicals which are bound to the ring atoms of the 5- or 6-membered rings are preferred in that inclusion of the substituents R⁵ and R⁵ may cause an undesired sterical interaction with internucleoside linkage. Thus, it is preferred that the one or two pairs of non-geminal substituents, which are constituting one or two biradical(s), respectively, are selected from the present substituents of R¹*, R⁴*, R⁶, R⁶*, R⁷, R⁷*, R^(N)*, and the ones of R², R²*, R³, and R³* not designating P*.

[0107] Preferably, the LNAs incorporated in the oligomers comprise only one biradical constituted by a pair of (two) non-geminal substituents. In particular, it is preferred that R³* designates P* and that the biradical is formed between R²* and R⁴* or R² and R³.

[0108] This being said, it should be understood (especially with due consideration of the known bi- and tricyclic nucleoside analogues—see “Background of the Invention”) that the present invention does not relate to oligomers comprising the following bi- or tricyclic nucleosides analogues:

[0109] (i) R² and R³ together designate a biradical selected from —O—CH₂—CH₂— and —O—CH₂—CH₂—CH₂— when LNA is a bicyclic nucleoside analogue;

[0110] (ii) R³ and R⁵ together designate a biradical selected from —CH₂—CH₂—, —O—CH₂—, when LNA is a bicyclic nucleoside analogue;

[0111] (iii) R³, R⁵, and R⁵* together designate a triradical —CH₂—CH(−)—CH₂— when LNA is a tricyclic nucleoside analogue;

[0112] (iv) R¹* and R⁶* together designate a biradical —CH₂— when LNA is a bicyclic nucleoside analogue; or

[0113] (v) R⁴* and R⁶* together designate a biradical —CH₂— when LNA is a bicyclic nucleoside analogue;

[0114] except where such bi- or tricyclic nucleoside analogues are combined with one or more of the novel LNAs defined herein.

[0115] In the present context, i.e. in the present description and claims, the orientation of the biradicals are so that the left-hand side represents the substituent with the lowest number and the right-hand side represents the substituent with the highest number, thus, when R³ and R⁵ together designate a biradical “—O—CH₂—”, it is understood that the oxygen atom represents R³, thus the oxygen atom is e.g. attached to the position of R³, and the methylene group represents R⁵.

[0116] Considering the numerous interesting possibilities for the structure of the biradical(s) in LNA(s) incorporated in oligomers according to the invention, it is believed that the biradical(s) constituted by pair(s) of non-geminal substituents preferably is/are selected from —(CR*R*)_(r)—Y—(CR*R*)_(s)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—Y—, —Y—(CR*R*)_(r+s)—Y—, —Y—(CR*R*)_(r)—Y—(CR*R*)_(s)—, —(CR*R*)_(r+s)—, —Y—, —Y—Y—, wherein each Y is independently selected from —O—, —S—, —Si(R*)₂—, —N(R*)—, >C═O, —C(═O)—N(R*)—, and —N(R*)—C(═O)—, each R* is independently selected from hydrogen, halogen, azido, cyano, nitro, hydroxy, mercapto, amino, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and/or two adjacent (non-geminal) R* may together designate a double bond; and each of r and s is 0-4 with the proviso that the sum r+s is 1-5. Particularly interesting situations are those wherein each biradical is independently selected from —Y—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—, and —Y—(CR*R*)_(r+s)—Y—, wherein and each of r and s is 0-3 with the proviso that the sum r+s is 1-4.

[0117] Considering the positioning of the biradical in the LNA(s), it is believed (based on the preliminary findings (see the examples)) that the following situations are especially interesting, namely where: R²* and R⁴* together designate a biradical selected from —Y—, —(CR*R*)_(r+s+1)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—, and —Y—(CR*R*)_(r+s)—Y—; R² and R³ together designate a biradical selected from —Y—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—, and —Y—(CR*R*)_(r+s)—Y—; R²* and R³ together designate a biradical selected from —Y—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—, and —Y—(CR*R*)_(r+s)—Y—; R³ and R⁴ together designate a biradical selected from —Y—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—, and —Y—(CR*R*)_(r+s)—Y—; R³ and R⁵ together designate a biradical selected from —Y′—, —(CR*R*)_(r+s+1)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—, and —Y—(CR*R*)_(r+s)—Y—; R¹* and R⁴* together designate a biradical selected from —Y′—, —(CR*R*)_(r+s+1)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—, and —Y—(CR*R*)_(r+s)—NR*—; or where R¹* and R²* together designate a biradical selected from —Y—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—, and —Y—(CR*R*)_(r+s)—Y—; wherein each of r and s is 0-3 with the proviso that the sum r+s is 1-4, Y is as defined above, and where Y′ is selected from —NR*—C(═O)— and —C(═O)—NR*—.

[0118] Particularly interesting oligomers are those wherein one of the following criteria applies for at least one LNA in an oligomer: R²* and R⁴* together designate a biradical selected from —O—, —S—, —N(R*)—, —(CR*R*)_(r+s+1)—, —(CR*R*)_(r)—O—(CR*R*)_(s)—,—(CR*R*)_(r)—S—(CR*R*)_(s)—, —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—, —O—(CR*R*)_(r+S)—O—, —S—(CR*R*)_(r+S)—O—, —O—(CR*R*)_(r+s)—S—, —N(R*)—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—N(R*)—, —S—(CR*R*)_(r+s)—S—, —N(R*)—(CR*R*)_(r+s)—N(R*)—, —N(R*)—(CR*R*)_(r+s)—S—, and —S—(CR*R*)_(r+s)—N(R*)—; R² and R³ together designate a biradical selected from —O—, —(CR*R*)_(r+s), —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(r)—; R²* and R³ together designate a biradical selected from —O—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—O—(CR*R()_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s); R³ and R⁴* together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; R³and R⁵ together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; R¹* and R⁴* together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; or R¹* and R²* together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; wherein each of r and s is 0-3 with the proviso that the sum r+s is 1-4, and where RH designates hydrogen or C₁₋₄-alkyl.

[0119] It is furthermore preferred that one R* is selected from hydrogen, hydroxy, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₆-alkyl, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and any remaining substituents R* are hydrogen.

[0120] In one preferred embodiment, one group R* in the biradical of at least one LNA is selected from DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands (where the latter groups may include a spacer as defined for the substituent B).

[0121] With respect to the substituents R¹*, R², R²*, R³, R⁴*, R⁵, R⁵*, R⁶ and R⁶*, R⁷, and R⁷*, which are present and not involved in P, P* or the biradical(s), these are independently selected from hydrogen, optionally substituted C₁₋₁₂-alkyl, optionally substituted C₂₋₁₂-alkenyl, optionally substituted C₂₋₁₂-alkynyl, hydroxy, C₁₋₁₂-alkoxy, C₂₋₁₂-alkenyloxy, carboxy, C₁₋₁₂-alkoxycarbonyl, C₁₋₁₂-alkylcarbonyl, formyl, aryl, aryloxy-carbonyl, aryloxy, arylcarbonyl, heteroaryl, heteroaryloxy-carbonyl, heteroaryloxy, heteroarylcarbonyl, amino, mono- and di(C₁₋₆-alkyl)amino, carbamoyl, mono- and di(C₁₋₆-alkyl)-amino-carbonyl, amino-C₁₋₆-alkyl-aminocarbonyl, mono- and di(C₁₋₆-alkyl)amino-C₁₋₆-alkyl-aminocarbonyl, C₁₋₆-alkyl-carbonylamino, carbamido, C₁₋₆-alkanoyloxy, sulphono, C₁₋₆-alkylsulphonyloxy, nitro, azido, sulphanyl, C₁₋₆-alkylthio, halogen, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands (where the latter groups may include a spacer as defined for the substituent B), where aryl and heteroaryl may be optionally substituted, and where two geminal substituents together may designate oxo, thioxo, imino, or optionally substituted methylene, or together may form a spiro biradical consisting of a 1-5 carbon atom(s) alkylene chain which is optionally interrupted and/or terminated by one or more heteroatoms/groups selected from —O—, —S—, and —(NR^(N))— where R^(N) is selected from hydrogen and C₁₋₄-alkyl, and where two adjacent (non-geminal) substituents may designate an additional bond resulting in a double bond; and R^(N)*, when present and not involved in a biradical, is selected from hydrogen and C₁₋₄-alkyl.

[0122] Preferably, each of the substituents R¹*, R², R²*, R³, R³*, R⁴*, R⁵, R⁵*, R⁶, R⁶*, R⁷, and R⁷* of the LNA(s), which are present and not involved in P, P* or the biradical(s), is independently selected from hydrogen, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, hydroxy, C₁₋₆-alkoxy, C₂₋₆-alkenyloxy, carboxy, C₁₋₆-alkoxycarbonyl, C₁₋₆-alkylcarbonyl, formyl, amino, mono- and di(C₁ ₆-alkyl)amino, carbamoyl, mono- and di(C₁₋₆-alkyl)-amino-carbonyl, C₁₋₆-alkyl-carbonylamino, carbamido, azido, C₁₋₆-alkanoyloxy, sulphono, sulphanyl, C₁₋₆-alkylthio, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and halogen, where two geminal substituents together may designate oxo, and where R^(N)*, when present and not involved in a biradical, is selected from hydrogen and C₁₋₄-alkyl.

[0123] In a preferred embodiment of the present invention, X is selected from —O—, —S—, and —NR^(N)*—, in particular —O—, and each of the substituents R¹*, R², R²*, R³, R³*, R⁴*, R⁵, R⁵*, R⁶, R⁶*, R⁷, and R⁷* of the LNA(s), which are present and not involved in P, P* or the biradical(s), designate hydrogen. In an even more preferred embodiment of the present invention, R²* and R⁴* of an LNA incorporated into an oligomer together designate a biradical. Preferably, X is O, R² selected from hydrogen, hydroxy, and optionally substituted C₁₋₆-alkoxy, and R¹*, R³, R⁵, and R⁵* designate hydrogen, and, more specifically, the biradical is selected from —O—, —(CH₂)₀₋₁—O—(CH₂)₁₋₃—, —(CH₂)₀₋₁—S—(CH₂)₁₋₃—, —(CH₂)₀₋₁—N(R^(N))—(CH₂)₁₋₃—, and —(CH₂)₂₋₄—, in particular from —O—CH₂—, —S—CH₂—, and —NR^(H)—CH₂—. Generally, with due regard to the results obtained so far, it is preferred that the biradical constituting R²* and R⁴* forms a two carbon atom bridge, i.e. the biradical forms a five membered ring with the furanose ring (X=O).

[0124] In another embodiment of the present invention, R² and R³ of an LNA incorporated into an oligomer together designate a biradical. Preferably, X is O, R²* is selected from hydrogen, hydroxy, and optionally substituted C₁₋₆-alkoxy, and R¹*, R⁴*, R⁵, and R⁵* designate hydrogen, and, more specifically, the biradical is selected from -(CH₂)₀₋₁—O—(CH₂)₁₋₃—, —(CH₂)₀₋₁—S—(CH₂)₁₋₃—, —(CH₂)₀₋₁—N(R^(H))—(CH₂)₁₋₃— and —(CH₂)₁₋₄—, in particular from —O—CH₂—, —S—CH₂—, —N(R^(H))—CH₂—. In the latter case, the amino and thio variants appears to be particularly interesting.

[0125] In a further embodiment of the present invention, R²* and R³ of an LNA incorporated into an oligomer together designate a biradical. Preferably, X is O, R² is selected from hydrogen, hydroxy, and optionally substituted C₁₋₆-alkoxy, and R¹*, R⁴*, R⁵, and R⁵* designate hydrogen, and, more specifically, the biradical is selected from —(CH₂)₀₋₁—O—(CH₂)₁₋₃— and —(CH₂)₂₋₄—.

[0126] In a further embodiment of the present invention, R³ and R⁴* of an LNA incorporated into an oligomer together designate a biradical. Preferably, X is O, R²* selected from hydrogen, hydroxy, and optionally substituted C₁₋₆-alkoxy, and R¹*, R², R⁵, and R⁵* designate hydrogen, and, more specifically, the biradical is —(CH₂)₀₋₂—O—(CH₂)₀₋₂—.

[0127] In a further embodiment of the present invention, R³ and R⁵* of an LNA incorporated into an oligomer together designate a biradical. Preferably, X is O, R²* selected from hydrogen, hydroxy, and optionally substituted C₁₆-alkoxy, and R¹, R², R⁴, and R⁵ designate hydrogen, and, more specifically, the biradical is selected from —O—(CHR*)₂₋₃——(CHR*)₁₋₃—O—(CHR*)₀₋₃—.

[0128] In a further embodiment of the present invention, R¹* and R⁴* of an LNA incorporated into an oligomer together designate a biradical. Preferably, X is O, R² selected from hydrogen, hydroxy, and optionally substituted C₁₋₆-alkoxy, and R², R³, R⁵, and R⁵ designate hydrogen, and, more specifically, the biradical is —(CH₂)₀₋₂—O—(CH₂)₀₋₂—.

[0129] In these embodiments, it is furthermore preferred that at least one LNA incorporated in an oligomer includes a nucleobase (substituent B) selected from adenine and guanine. In particular, it is preferred that an oligomer have LNA incorporated therein both include at least one nucleobase selected from thymine, urasil and cytosine and at least one nucleobase selected from adenine and guanine. For LNA monomers, it is especially preferred that the nucleobase is selected from adenine and guanine.

[0130] For these interesting embodiments, it is also preferred that the LNA(s) has/have the general formula la (see below).

[0131] Within a variant of these interesting embodiments, all monomers of a oligonucleotide are LNA monomers.

[0132] As it will be evident from the general formula I (LNA(s) in an oligomer) (and the general formula II (monomeric LNA)—see below) and the definitions associated therewith, there may be one or several asymmetric carbon atoms present in the oligomers (and monomeric LNAS) depending on the nature of the substituents and possible biradicals, cf. below. The oligomers prepared according to the method of the invention, as well as the oligomers per se, are intended to include all stereoisomers arising from the presence of any and all isomers of the individual monomer fragments as well as mixtures thereof, including racemic mixtures. When considering the 5- or 6-membered ring, it is, however, believed that certain stereochemical configurations will be especially interesting, e.g. the following

[0133] where the wavy lines represent the possibility of both diastereomers arising from the interchange of the two substituents in question.

[0134] An especially interesting stereoisomeric representation is the case where the LNA(s) has/have the following formula Ia

[0135] Also interesting as a separate aspect of the present invention is the variant of formula Ia where B is in the “α-configuration”.

[0136] In these cases, as well as generally, R³* preferably designates P*.

[0137] The oligomers according to the invention typically comprise 1-10000 LNA(s) of the general formula I (or of the more detailed general formula Ia) and 0-10000 nucleosides selected from naturally occurring nucleosides and nucleoside analogues. The sum of the number of nucleosides and the number of LNA(s) is at least 2, preferably at least 3, in particular at least 5, especially at least 7, such as in'the range of 2-15000, preferably in the range of 2-100, such as 3-100, in particular in the range of 2-50, such as 3-50 or 5-50 or 7-50.

[0138] Preferably at least one LNA comprises a nucleobase as the substituent B.

[0139] In the present context, the term “nucleoside” means a glycoside of a heterocyclic base. The term “nucleoside” is used broadly as to include non-naturally occurring nucleosides, naturally occurring nucleosides as well as other nucleoside analogues. Illustrative examples of nucleosides are ribonucleosides comprising a ribose moiety as well as deoxyribonuclesides comprising a deoxyribose moiety. With respect to the bases of such nucleosides, it should be understood that this may be any of the naturally occurring bases, e.g. adenine, guanine, cytosine, thymine, and uracil, as well as any modified variants thereof or any possible unnatural bases.

[0140] When considering the definitions and the known nucleosides (naturally occurring and non-naturally occurring) and nucleoside analogues (including known bi- and tricyclic analogues), it is clear that an oligomer may comprise one or more LNA(s) (which may be identical or different both with respect to the selection of substituent and with respect to selection of biradical) and one or more nucleosides and/or nucleoside analogues. In the present context “oligonucleotide” means a successive chain of nucleosides connected via internucleoside linkages, however, it should be understood that a nucleobase in one or more nucleotide units (monomers) in an oligomer (oligonucleotide) may have been modified with a substituent B as defined above.

[0141] The oligomers may be linear, branched or cyclic. In the case of a branched oligomer, the branching points may be located in a nucleoside, in an internucleoside linkage or, in an intriguing embodiment, in an LNA. It is believed that in the latter case, the substituents R², R²*, R³, and R³* may designate two groups P* each designating an internucleoside linkage to a preceding monomer, in particular, one of R² and R²* designate P* and one or R³ and R³* designate a further P*.

[0142] As mentioned above, the LNA(s) of an oligomer are connected with other monomers via an internucleoside linkage. In the present context, the term “internucleoside linkage” means a linkage consisting of 2 to 4, preferably 3, groups/atoms selected from —CH₂—, —O—, —S—, —NR^(H)—, >C═O, >C═NR^(H), >C═S, —Si(R″)₂—, —SO—, —S(O)₂—, —P(O)₂—, —PO(BH₃)—, —P(O,S)—, —P(S)₂—, —PO(R″)—, —PO(OCH₃)—, and —PO(NHR^(H))—, where R^(H) is selected form hydrogen and C₁₋₄-alkyl, and R″ is selected from C₁₋₆-alkyl and phenyl. Illustrative examples of such internucleoside linkages are —CH₂—CH₂—CH₂—,—CH₂—CO—CH₂—, —CH₂—CHOH—CH₂—, —O—CH₂—O—, —O—CH₂—CH₂—, —O—CH₂—CH═ (including R⁵ when used as a linkage to a succeeding monomer), —CH₂—CH₂—O—, —NR^(H)—CH₂—CH₂—, —CH₂—CH₂—NR^(H)—, —CH₂—NR^(H)—CH₂—, —O—CH₂—CH₂—NR^(H)—, —NR^(H)—CO—O—, —NR^(H)—CO—NR^(H), —NR^(H)—CS—NR^(H), —NR^(H)—C(═NR^(H))—NR^(H)—, —NR^(H)—CO—CH₂—NR^(H), —O—CO—O—, —O—CO—CH₂—O—, —O—CH₂—CO—O—, —CH₂CO—NR^(H)—, —O—CO—NR^(H), —NR^(H)—CO—CH₂—, —O—CH₂—CO—NR^(H)—, —O—CH₂—CH₂—NR^(H)—, —CH═N—O—, —CH₂—NR^(H)—O—, —CH₂—O—N═ (including R⁵ when used as a linkage to a succeeding monomer), CH₂—O—NR^(H)—, —CO—NR^(H)—CH₂—, —CH₂—NR^(H)O—, —CH₂—NR^(H)—CO—, —O—NR^(H)—CH₂—, —O—NR^(H)—, —O—CH₂—S—, —S—CH₂—O—, —CH₂—CH₂—S—, —O—CH₂—CH₂—S—, —S—CH₂—CH (including R⁵ when used as a linkage to a succeeding monomer), —S—CH₂—CH₂—, —S—CH₂—CH₂—O—, —S—CH₂—CH₂—S—, —CH₂—S—CH₂—, —CH₂—SO—CH₂—, —CH₂—SO₂—CH₂—, —O—SO—O—, —O—S(O)2—O—, —O—S(O)₂—CH₂—, —O—S(O)₂—NR^(H), —NR^(H)—S(O)₂—CH₂—, —O—S(O)₂—CH₂—, —O—P(O)₂—O—, —O—P(O,S)—O—, —O—P(S)₂—O—, —S—P(O)₂—O—, —S—P(O,S)—O—, —S—P(S)₂—O—, —O—P(O)₂—S—, —O—P(O,S)—S—, —O—P(S)₂—S—, —S—P(O)₂—S—, —S—P(O,S)—S—, —S—P(S)₂—S—, —O—PO(R″)—O—, —O—PO(OCH₃)—O—, —O—PO(OCH₂CH₃)—O—, —O—PO(OCH₂CH₂S—R)—O—, —O—PO(BH₃)—O—, —O—PO(NHR^(N))O, —O—P(O)₂—NR^(H)—, —NR^(H)—P(O)₂—O—, —O—P(O,NR^(H))—O—, —CH₂—P(O)₂—O—, —O—P(O)₂—CH₂—, and —O—Si(R″)₂—O—; among which —CH₂—CO—NR^(H)—, —CH₂—NR^(H)—O—, —S—CH₂—O—, —O—P(O)₂—O—, —O—P(O,S)—O—, —O—P(S)₂—O—, —NR^(H)—P(O)₂—O—, —O—P(O,NR^(H))—O—, —O—PO(R″)—O—, —O—PO(CH₃)—O—, and —O—PO(NHR^(N))—O—, where R^(H) is selected form hydrogen and C₁₋₄—alkyl, and R″ is selected from C₁₋₆—alkyl and phenyl, are especially preferred. Further illustrative examples are given in Mesmaeker et. al., Current Opinion in Structural Biology 1995, 5, 343-355. The left-hand side of the internucleoside linkage is bound to the 5- or 6-membered ring as substituent P*, whereas the right-hand side is bound to the 5′-position of a preceding monomer.

[0143] It is also clear from the above that the group P may also designate a 5′-terminal group in the case where the LNA in question is the 5′-terminal monomer. Examples of such 5′-terminal groups are hydrogen, hydroxy, optionally substituted C₁₋₆-alkyl, optionally substituted C₁₋₃-alkoxy, optionally substituted C₁₋₆-alkylcarbonyloxy, optionally substituted aryloxy, monophosphate, diphosphate, triphosphate, and —W—A′, wherein W is selected from —O—, —S—, and —N(R^(H)) where R^(H) is selected from hydrogen and C₁₋₆-alkyl, and where A′ is selected from DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands (where the latter groups may include a spacer as defined for the substituent B).

[0144] In the present description and claims, the terms “monophosphate”, “diphosphate”, and “triphosphate” mean groups of the formula: —O—P(O)₂—O⁻, —O—P(O)₂—O—P(O)₂—O⁻, and —O—P(O)₂—O—P(O)₂—O—P(O)₂—O⁻, respectively.

[0145] In a particularly interesting embodiment, the group P designates a 5′-terminal groups selected from monophosphate, diphosphate and triphosphate. Especially the triphosphate variant is interesting as a substrate

[0146] Analogously, the group P* may designate a 3′-terminal group in the case where the LNA in question is the 3′-terminal monomer. Examples of such 3′-terminal groups are hydrogen, hydroxy, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkylcarbonyloxy, optionally substituted aryloxy, and —W—A′, wherein W is selected from —O—, —S—, and —N(R^(H)) where R^(H) is selected from hydrogen and C₁₋₆-alkyl, and where A′ is selected from DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands (where the latter groups may include a spacer as defined for the substituent B).

[0147] In a preferred embodiment of the present invention, the oligomer has the following formula V:

G-[Nu-L]_(n(0))-{[LNA-L]_(m(q))-[Nu-L]_(n(q))}_(q)-G*  V

[0148] wherein

[0149] q is 1-50;

[0150] each of n(0), . . . , n(q) is independently 0-10000;

[0151] each of m(1), . . . , m(q) is independently 1-10000;

[0152] with the proviso that the sum of n(0), . . . , n(q) and m(1), . . . , m(q) is 2-15000;

[0153] G designates a 5′-terminal group;

[0154] each Nu independently designates a nucleoside selected from naturally occurring nucleosides and nucleoside analogues;

[0155] each LNA independently designates a nucleoside analogue;

[0156] each L independently designates an internucleoside linkage between two groups selected from Nu and LNA, or L together with G* designates a 3′-terminal group; and

[0157] each LNA-L independently designates a nucleoside analogue of the general formula I as defined above, or preferably of the general formula Ia as defined above.

[0158] Within this embodiment, as well as generally, the present invention provides the intriguing possibility of including LNAs with different nucleobases, in particular both nucleobases selected from thymine, cytosine and urasil and nucleobases selected from adenine and guanine.

[0159] In another embodiment of the present invention, the oligomer further comprises a PNA mono- or oligomer segment of the formula

[0160] wherein B is a defined above for the formula I, AASC designates hydrogen or an amino acid side chain, t is 1-5, and w is 1-50.

[0161] In the present context, the term “amino acid side chain” means a group bound to the α-atom of an α-amino acids, i.e. corresponding to the α-amino acid in question without the glycine moiety, preferably an either naturally occurring or a readily available α-amino acid. Illustrative examples are hydrogen (glycine itself), deuterium (deuterated glycine), methyl (alanine), cyanomethyl (α-cyano-alanine), ethyl, 1-propyl (norvaline), 2-propyl (valine), 2-methyl-1-propyl (leucine), 2-hydroxy-2-methyl-l-propyl (β-hydroxy-leucine), 1-butyl (norleucine), 2-butyl (isoleucine), methylthioethyl (methionine), benzyl (phenylalanine), p-amino-benzyl (p-amino-phenylalanine), p-iodo-benzyl (p-iodo-phenylalanine), p-fluoro-benzyl (p-fluoro-phenylalanine), p-bromo-benzyl (p-bromo-phenylalanine), p-chloro-benzyl (p-chloro-phenylalanine), p-nitro-benzyl (p-nitro-phenylalanine), 3-pyridylmethyl (β-(3-pyridyl)-alanine), 3,5-diiodo-4-hydroxy-benzyl (3,5-diiodo-tyrosine), 3,5-dibromo-4-hydroxy-benzyl (3,5-dibromo-tyrosine), 3,5-dichloro-4-hydroxy-benzyl (3,5-dichloro-tyrosine), 3,5-difluoro-4-hydroxy-benzyl (3,5-difluoro-tyrosine), 4-methoxy-benzyl (O-methyl-tyrosine), 2-naphtylmethyl (β-(2-naphtyl)-alanine), 1-naphtylmethyl (β-(1-naphtyl)-alanine), 3-indolylmethyl (tryptophan), hydroxymethyl (serine), 1-hydroxyethyl (threonine), mercaptomethyl (cysteine), 2-mercapto-2-propyl (penicillamine), 4-hydroxybenzyl (tyrosine), amino-carbonylmethyl (asparagine), 2-aminocarbonylethyl (glutamine), carboxymethyl (aspartic acid), 2-carboxyethyl (glutamic acid), aminomethyl (α,β-diaminopropionic acid), 2-aminoethyl (α,γ-diaminobutyric acid), 3-amino-propyl (ornithine), 4-amino-1-butyl (lysine), 3-guanidino-1-propyl (arginine), and 4-imidazolylmethyl (histidine).

[0162] PNA mono- or oligomer segment may be incorporated in a oligomer as described in EP 0672677 A2.

[0163] The oligomers of the present invention are also intended to cover chimeric oligomers. “Chimeric oligomers” means two or more oligomers with monomers of different origin joined either directly or via a spacer. Illustrative examples of such oligomers which can be combined are peptides, PNA-oligomers, oligomers containing LNA's, and oligonucleotide oligomers.

[0164] Apart from the oligomers defined above, the present invention also provides monomeric LNAs useful, e.g., in the preparation of oligomers, as substrates for, e.g., nucleic acid polymerases, polynucleotide kinases, terminal transferases, and as therapeutical agents, see further below. The monomeric LNAs correspond in the overall structure (especially with respect to the possible biradicals) to the LNAs defined as constituents in oligomers, however with respect to the groups P and P*, the monomeric LNAs differ slightly as will be explained below. Furthermore, the monomeric LNAs may comprise functional group protecting groups, especially in the cases where the monomeric LNAs are to be incorporated into oligomers by chemical synthesis.

[0165] An interesting subgroup of the possible monomeric LNAs comprises bicyclic nucleoside analogues (LNAs) of the general formula II

[0166] wherein the substituent B is selected from nucleobases, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands; X is selected from —O—, —S—, —N(R^(N)*)—, and —C(R⁶R⁶*)—, preferably from —O—, —S—, and —N(R^(N)*); one of the substituents R², R²*, R³, and R³* is a group Q*;

[0167] each of Q and Q* is independently selected from hydrogen, azido, halogen, cyano, nitro, hydroxy, Prot-O—, Act-O—, mercapto, Prot-S—, Act-S—, C₁₋₆-alkylthio, amino, Prot-N(R^(H))—, Act-N(R^(H))—, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyl, optionally substituted C₂₋₆-alkynyloxy, monophosphate, diphosphate, triphosphate, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, ligands, carboxy, sulphono, hydroxymethyl, Prot-O-CH₂—, Act-O—CH₂—, aminomethyl, Prot-N(R^(H))—CH₂—, Act-N(R^(H))—CH₂—, carboxymethyl, sulphonomethyl, where Prot is a protection group for —OH, —SH, and —NH(R^(H)), respectively, Act is an activation group for —OH, —SH, and —NH(R^(H)), respectively, and R^(H) is selected from hydrogen and C₁₋₆-alkyl;

[0168] R²* and R⁴* together designate a biradical selected from —O—, —S—, —N(R*)—, —(CR*R*)_(r+s+1)—, —(CR*R*)_(r)—O—(CR*R*)_(s)—,—(CR*R*)_(r)—S—(CR*R*)_(s)—, —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—,—O—(CR*R*)_(r+s)—O—, —S—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—S—, —N(R*)—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—N(R*)—, —S—(CR*R*)_(r+s)—S—, —N(R*)—(CR*R*)_(r+s)—N(R*)—, —N(R*)—(CR*R*)_(r+s)—S—, and —S—(CR*R*)_(r+s)—N(R*)—; R² and R³ together designate a biradical selected from —O—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; R²* and R³ together designate a biradical selected from —O—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; R³ and R⁴* together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; R³ and R⁵ together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(r)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; R¹* and R⁴* together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; or R¹* and R²* together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; wherein R* is as defined above for the oligomers; and each of the substituents R¹*, R², R²*, R³, R⁴*, R⁵, and R⁵*, which are not involved in Q, Q* or the biradical, are as defined above for the oligomers.

[0169] It should furthermore be understood, with due consideration of the known bicyclic nucleoside analogues, that R³ and R⁵ do not together designate a biradical selected from —CH₂—CH₂—, —O—CH₂—, and —O—Si(^(i)Pr)₂—O—Si(^(i)Pr)₂—O—.

[0170] The monomeric LNAs also comprise basic salts and acid addition salts thereof. Furthermore, it should be understood that any chemical group (including any nucleobase), which is reactive under the conditions prevailing in chemical oligonucleotide synthesis, is optionally functional group protected as known in the art. This means that groups such as hydroxy, amino, carboxy, sulphono, and mercapto groups, as well as nucleobases, of a monomeric LNA are optionally functional group protected. Protection (and deprotection) is performed by methods known to the person skilled in the art (see, e.g., Greene, T. W. and Wuts, P. G. M., “Protective Groups in Organic Synthesis”, 2^(nd) ed., John Wiley, N.Y. (1991), and M. J. Gait, Oligonucleotide Synthesis, IRL Press, 1984).

[0171] Illustrative examples of hydroxy protection groups are optionally substituted trityl, such as 4,4′-dimethoxytrityl (DMT), 4-monomethoxytrityl (MMT), and trityl, optionally substituted 9-(9-phenyl)xanthenyl (pixyl), optionally substituted ethoxycarbonyloxy, p-phenylazophenyloxycarbonyloxy, tetraahydropyranyl (thp), 9-fluorenylmethoxycarbonyl (Fmoc), methoxytetrahydropyranyl (mthp), silyloxy such as trimethylsilyl (TMS), triisopropylsilyl (TIPS), tert-butyldimethylsilyl (TBDMS), triethylsilyl, and phenyidimethylsilyl, benzyloxycarbonyl or substituted benzyloxycarbonyl ethers such as 2-bromo benzyloxycarbonyl, tert-butylethers, alkyl ethers such as methyl ether, acetals (including two hydroxy groups), acyloxy such as acetyl or halogen substituted acetyls, e.g. chloroacetyl or fluoroacetyl, isobutyryl, pivaloyl, benzoyl and substituted benzoyls, methoxymethyl (MOM), benzyl ethers or substituted benzyl ethers such as 2,6-dichlorobenzyl (2,6-Cl₂Bzl). Alternatively, the hydroxy group may be protected by attachment to a solid support optionally through a linker.

[0172] Illustrative examples of amino protection groups are Fmoc (fluorenylmethoxycarbonyl), BOC (tert-butyloxycarbonyl), trifluoroacetyl, allyloxycarbonyl (alloc, AOC), benzyloxycarbonyl (Z, Cbz), substituted benzyloxycarbonyls such as 2-chloro benzyloxycarbonyl ((2-CIZ), monomethoxytrityl (MMT), dimethoxytrityl (DMT), phthaloyl, and 9-(9-phenyl)xanthenyl (pixyl).

[0173] Illustrative examples of carboxy protection groups are allyl esters, methyl esters, ethyl esters, 2-cyanoethylesters, trimethylsilylethylesters, benzyl esters (Obzl), 2-adamantyl esters (O-2-Ada), cyclohexyl esters (OcHex), 1,3-oxazolines, oxazoler, 1,3-oxazolidines, amides or hydrazides.

[0174] Illustrative examples of mercapto protecting groups are trityl (Trt), acetamidomethyl (acm), trimethylacetamidomethyl (Tacm), 2,4,6-trimethoxybenzyl (Tmob), tert-butylsulfenyl (StBu), 9-fluorenylmethyl (Fm), 3-nitro-2-pyridinesulfenyl (Npys), and 4-methylbenzyl (Meb).

[0175] Furthermore, it may be necessary or desirable to protect any nucleobase included in an monomeric LNA, especially when the monomeric LNA is to be incorporated in an oligomer according to the invention. In the present context, the term “protected nucleobases” means that the nucleobase in question is carrying a protection group selected among the groups which are well-known for a man skilled in the art (see e.g. Protocols for Oligonucleotides and Analogs, vol 20, (Sudhir Agrawal, ed.), Humana Press, 1993, Totowa, N.J.; S. L. Beaucage and R. P. Iyer, Tetrahedron, 1993, 49, 6123; S. L. Beaucage and R. P. Iyer, Tetrahedron, 1992, 48, 2223; and E. Uhlmann and A. Peyman, Chem. Rev., 90, 543.). Illustrative examples are benzoyl, isobutyryl, tert-butyl, tert-butyloxycarbonyl, 4-chloro-benzyloxycarbonyl, 9-fluorenylmethyl, 9-fluorenylmethyloxycarbonyl, 4-methoxybenzoyl, 4-methoxytriphenylmethyl, optionally substituted triazolo, p-toluenesulphonyl, optionally substituted sulphonyl, isopropyl, optionally substituted amidines, optionally substituted trityl, phenoxyacetyl, optionally substituted acyl, pixyl, tetrahydropyranyl, optionally substituted silyl ethers, and 4-methoxybenzyloxycarbonyl. Chapter 1 in “Protocols for oligonucleotide conjugates”, Methods in Molecular Biology, vol 26, (Sudhir Agrawal, ed.), Humana Press, 1993, Totowa, N.J. and S. L. Beaucage and R. P. Iyer, Tetrahedron, 1992, 48, 2223 disclose further suitable examples.

[0176] In a preferred embodiment, the group B in a monomeric LNA is preferably selected from nucleobases and protected nucleobases.

[0177] In an embodiment of the monomeric LNAs according to the present invention, one of Q and Q*, preferably Q*, designates a group selected from Act-O—, Act-S—, Act-N(R^(H))—, Act-O—CH₂—, Act-S—CH₂—, Act-N(R^(H))—CH₂—, and the other of Q and Q*, preferably Q, designates a group selected from hydrogen, azido, halogen, cyano, nitro, hydroxy, Prot-O—, mercapto, Prot-S—, C₁₋₆-alkylthio, amino, Prot-N(R^(H)), mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyl, optionally substituted C₂₋₆-alkynyloxy, monophosphate, diphosphate, triphosphate, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, ligands, carboxy, sulphono, hydroxymethyl, Prot-O—CH₂—, aminomethyl, Prot-N(R^(H))—CH₂—, carboxymethyl, sulphonomethyl, and R^(H) is selected from hydrogen and C₁₋₆-alkyl.

[0178] In the case described above, the group Prot designates a protecting group for —OH, —SH, and —NH(R^(H)), respectively. Such protection groups are selected from the same as defined above for hydroxy protection groups, mercapto protection group, and amino protection groups, respectively, however taking into consideration the need for a stable and reversible protection group. However, it is preferred that any protection group for —OH is selected from optionally substituted trityl, such as dimethoxytrityl (DMT), monomethoxytrityl (MMT), and trityl, and 9-(9-phenyl)xanthenyl (pixyl), optionally substituted, tetrahydropyranyl (thp) (further suitable hydroxy protection groups for phosphoramidite oligonucleotide synthesis are described in Agrawal, ed. “Protocols for Oligonucleotide Conjugates”; Methods in Molecular Biology, vol. 26, Humana Press, Totowa, N.J. (1 994) and Protocols for Oligonucleotides and Analogs, vol 20, (Sudhir Agrawal, ed.), Humana Press, 1993, Totowa, N.J.), or protected as acetal; that any protection group for —SH is selected from trityl, such as dimethoxytrityl (DMT), monomethoxytrityl (MMT), and trityl, and 9-(9-phenyl)xanthenyl (pixyl), optionally substituted, tetrahydropyranyl (thp) (further suitable mercapto protection groups for phosphoramidite oligonucleotide synthesis are also described in Agrawal (see above); and that any protecting group for —NH(R^(H)) is selected from trityl, such as dimethoxytrityl (DMT), monomethoxytrityl (MMT), and trityl, and 9-(9-phenyl)xanthenyl (pixyl), optionally substituted, tetrahydropyranyl (thp) (further suitable amino protection groups for phosphoramidite oligonucleotide synthesis are also described in Agrawal (see above).

[0179] In the embodiment above, as well as for any monomeric LNAs defined herein, Act designates an activation group for —OH, —SH, and —NH(R^(H)), respectively. Such activation groups are, e.g., selected from optionally substituted O-phosphoramidite, optionally substituted O-phosphortriester, optionally substituted O-phosphordiester, optionally substituted H-phosphonate, and optionally substituted O-phosphonate.

[0180] In the present context, the term “phosphoramidite” means a group of the formula —P(OR^(x))—N(R^(v))₂, wherein R^(x) designates an optionally substituted alkyl group, e.g. methyl, 2-cyanoethyl, or benzyl, and each of R^(v) designate optionally substituted alkyl groups, e.g. ethyl or isopropyl, or the group —N(R^(v))₂ forms a morpholino group (—N(CH₂CH₂)₂O). R^(x) preferably designates 2-cyanoethyl and the two R^(v) are preferably identical and designate isopropyl. Thus, an especially relevant phosphoramidite is N,N-diisopropyl-O-(2-cyanoethyl)phosphoramidite.

[0181] It should be understood that the protecting groups used herein for a single monomeric LNA or several monomeric LNAs may be selected so that when this/these LNA(s) are incorporated in an oligomer according to the invention, it will be possible to perform either a simultaneous deprotection or a sequential deprotection of the functional groups. The latter situation opens for the possibility of regioselectively introducing one or several “activelfunctional” groups such as DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, where such groups may be attached via a spacer as described above.

[0182] In a preferred embodiment, Q is selected from hydrogen, azido, halogen, cyano, nitro, hydroxy, Prot-O—, mercapto, Prot-S—, C₁₋₆-alkylthio, amino, Prot-N(R^(H)), mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyl, optionally substituted C₂₋₆-alkynyloxy, monophosphate, diphosphate, triphosphate, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, ligands, carboxy, sulphono, hydroxymethyl, Prot-O—CH₂—, aminomethyl, Prot-N(R^(H))—CH₂—, carboxymethyl, sulphonomethyl, where Prot is a protection group for —OH, —SH, and —NH(R^(H)), respectively, and R^(H) is selected from hydrogen and C₁₋₆-alkyl; and Q* is selected from hydrogen, azido, halogen, cyano, nitro, hydroxy, Act-O—, mercapto, Act-S—, C₁₋₆-alkylthio, amino, Act-N(R^(H))—, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyl, optionally substituted C₂₋₆-alkynyloxy, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, ligands, carboxy, sulphono, where Act is an activation group for —OH, —SH, and —NH(R^(H)), respectively, and R^(H) is selected from hydrogen and C₁₋₆-alkyl.

[0183] The monomeric LNAs of the general formula II may, as the LNAs incorporated into oligomers, represent various stereoisomers. Thus, the stereochemical variants described above for the LNAs incorporated into oligomers are believed to be equally applicable in the case of monomeric LNAs (however, it should be noted that P should then be replaced with Q).

[0184] In a preferred embodiment of the present invention, the monomeric LNA has the general formula IIa

[0185] wherein the substituents are defined as above.

[0186] Furthermore, with respect to the definitions of substituents, biradicals, R*, etc. the same preferred embodiments as defined above for the oligomer according to the invention also apply in the case of monomeric LNAs.

[0187] In a particularly interesting embodiment of the monomeric LNAs of the present invention, B designates a nucleobase, preferably a nucleobase selected from thymine, cytosine, urasil, adenine and guanine (in particular adenine and guanine), X is —O—, R²* and R⁴* together designate a biradical selected from —(CH₂)₀₋₁—O—(CH₂)₁₋₃—, —(CH₂)₀₋₁—S—(CH₂)₁₋₃—, and —(CH₂)₀₋₁N(R^(N))(CH₂)₁₋₃—, in particular —O—CH₂—, —S—CH₂— and R^(N)—CH₂—, where R^(N) is selected from hydrogen and C₁₋₄-alkyl, Q designates Prot-O—, R³ is Q* which designates Act-OH, and R¹*, R², R³, R⁵, and R⁵* each designate hydrogen. In this embodiment, R^(N) may also be selected from DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups and ligands.

[0188] In a further particularly interesting embodiment of the monomeric LNAs of the present invention, B designates a nucleobase, preferably a nucleobase selected from thymine, cytosine, urasil, adenine and guanine (in particular adenine and guanine), X is —O—, R²* and R⁴* together designate a biradical selected from —(CH₂)₀₋₁—O—(CH₂)₁₋₃—, —(CH₂)₀₋₁—S—(CH₂)₁₋₃—, and —(CH₂)₀₋₁—N(R^(N))—(CH₂)₁₋₃—, in particular —O—CH₂—, —S—CH₂— and —RN—CH₂—, where R^(N) is selected from hydrogen and C₁₋₄-alkyl, Q is selected from hydroxy, mercapto, C₁₋₆-alkylthio, amino, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyloxy, monophosphate, diphosphate, and triphosphate, R³ is Q* which is selected from hydrogen, azido, halogen, cyano, nitro, hydroxy, mercapto, C₁₋₆-alkylthio, amino, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyl, and optionally substituted C₂₋₆-alkynyloxy, R³ is selected from hydrogen, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, and optionally substituted C₂₋₆-alkynyl, and R¹*, R², R⁵, and R⁵* each designate hydrogen. Also here, R^(N) may also be selected from DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups and ligands.

[0189] In a further particularly interesting embodiment of the monomeric LNAs of the present invention, B designates a nucleobase, X is —O—, R² and R³together designate a biradical selected from —(CH₂)₀₋₁—O—CH═CH—, —(CH₂)₀₋₁—S—CH═CH—, and —(CH₂)₀₋₁—N(RN)—CH═CH— where R^(N) is selected from hydrogen and C₁₋₄-alkyl, Q is selected from hydroxy, mercapto, C₁₋₆-alkylthio, amino, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyloxy, monophosphate, diphosphate, and triphosphate, R³* is Q* which is selected from hydrogen, azido, halogen, cyano, nitro, hydroxy, mercapto, C₁₋₆-alkylthio, amino, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyl, and optionally substituted C₂₋₆-alkynyloxy, and R¹*, R²*, R⁴*, R⁵, and R⁵* each designate hydrogen.

[0190] One aspect of the invention is to provide various derivatives of LNAs for solid-phase and/or solution phase incorporation into an oligomer. As an illustrative example, monomers suitable for incorporation of (1S,3R,4R,7S)-7-hydroxy-1-hydroxymethyl-3-(thymin-1-yl)-2,5-dioxabicyclo[2.2.1]heptane, (1S,3R,4R,7S)-7-hydroxy-1-hydroxymethyl-3-(cytosin-1-yl)-2,5-dioxabicyclo[2. 2.1 ]heptane, (1S,3R,4R,7S)-7-hydroxy-1-hydroxymethyl-3-(urasil-1-yl)-2,5-dioxabicyclo[2.2.1]heptane, (1S,3R,4R,7S)-7-hydroxy-1-hydroxymethyl-3-(guanin-1-yl)-2,5-dioxabicyclo-[2.2.1]heptane, and (1S,3R,4R,7S)-7-hydroxy-1-hydroxymethyl-3-(adenin-1-yl)-2,5-dioxabicyclo[2.2.1]heptane using the phosphoramidite approach, the phosphortriester approach, and the H-phosphonate approach, respectively, are (1R,3R,4R,7S)-7-(2-Cyanoethoxy(diisopropylamino)phosphinoxy)-1-(4,4′-dimethoxytrityloxymethyl)-3-(thymin-1-yl)-2,5-dioxabicyclo[2.2.1]heptane, (1R,3R,4R,7S)-7-hydroxy-1-(4,4′-di-methoxytrityloxymethyl)-3-(thymin-1-yl)-2,5-dioxabicyclo[2.2.1]heptane-7-O-(2-chlorophenylphosphate), and (1R,3R,4R,7S)-7-hydroxy-1-(4,4′-dimethoxytrityloxymethyl)-3-(thymin-1-yl)-2,5-dioxabicyclo[2.2.1]heptane-7-O-(H-phosphonate) and the 3-(cytosin-1-yl), 3-(urasil-1-yl), 3-(adenin-1-yl) and 3-(guanin-1-yl) analogues thereof, respectively. Furthermore, the analogues where the methyleneoxy biradical of the monomers is substituted with a methylenethio, a methyleneamino, or a 1,2-ethylene biradical are also expected to constitute particularly interesting variants within the present invention. The methylenethio and methyleneamino analogues are believed to equally applicable as the methyleneoxy analogue and therefore the specific reagents corresponding to those mentioned for incorporation of (1S,3R,4R,7S)-7-hydroxy-1-hydroxymethyl-3-(thymin-1-yl)-2,5-dioxa-bicyclo[2.2.1]heptane, (1S,3R,4R,7S)-7-hydroxy-1-hydroxymethyl-3-(cytosin-1-yl)-2,5-dioxabicyclo[2.2.1]heptane, (1S,3R,4R,7S)-7-hydroxy-1-hydroxymethyl-3-(urasil-1-yl)-2,5-dioxabicyclo[2.2.1]heptane, (1S,3R,4R,7S)-7-hydroxy-1-hydroxymethyl-3-(guanin-1-yl) -2,5-dioxabicyclo[2.2.1]heptane, and (1S,3R,4R,7S)-7-hydroxy-1-hydroxymethyl-3-(adenin-1-yl)-2,5-dioxabicyclo[2.2.1]heptane should also be considered as particularly interesting reactive monomers within the present invention. For the methyleneamine analogue, it should be noted that the secondary amine may carry a substituent selected from optionally substituted C₁₋₆-alkyl such as methyl and benzyl, optionally substituted Cl₆-alkylcarbonyl such as trifluoroacetyl, optionally substituted arylcarbonyl and optionally substituted heteroarylcarbonyl.

[0191] In a particularly interesting embodiment, the present invention relates to an oligomer comprising at least one LNA of the general formula Ia

[0192] wherein X is —O—; B is selected from nucleobases, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands; P designates the radical position for an internucleoside linkage to a succeeding monomer, or a 5′-terminal group, such internucleoside linkage or 5′-terminal group optionally including the substituent R⁵; R³* is a group P* which designates an internucleoside linkage to a preceding monomer, or a 3′-terminal group; R²* and R⁴* together designate a biradical selected from —O—, —S, —N(R*)—, —(CR*R*)_(r+s+1)—, —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—, —O—(CR*R*)_(r+s)—O—, —S—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—S—,—N(R*)—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—N(R*)—, —S—(CR*R*)^(r+s)—S—, —N(R*)—(CR*R*)_(r+s)—N(R*)—, —N(R*)—(CR*R*)_(r+s)—S—, and —S—(CR*R*)_(r+s)—N(R*)—; wherein each R* is independently selected from hydrogen, halogen, azido, cyano, nitro, hydroxy, mercapto, amino, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁ ₆-alkoxy, optionally substituted C₁₋₆-alkyl, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and/or two adjacent (non-geminal) R* may together designate a double bond, and each of r and s is 0-3 with the proviso that the sum r+s is 1-4; each of the substituents R¹*, R², R³, R⁵, and R⁵* is independently selected from hydrogen, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, hydroxy, C₁₋₆-alkoxy, C₂₋-alkenyloxy, carboxy, C₁₋₆-alkoxycarbonyl, C₁₋₆-alkylcarbonyl, formyl, amino, mono- and di(C₁₋₆-alkyl)amino, carbamoyl, mono- and di(C₁₋₆-alkyl)-amino-carbonyl, C₁₋₆-alkyl-carbonylamino, carbamido, azido, C₁₋₆-alkanoyloxy, sulphono, sulphanyl, C₁₋₆-alkylthio, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and halogen, where two geminal substituents together may designate oxo; and basic salts and acid addition salts thereof. In particular, one R* is selected from hydrogen, hydroxy, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and any remaining substituents R* are hydrogen. Especially, the biradical is selected from —O—, —(CH₂)₀₋₁—O—(CH₂)₁₋₃—, —(CH₂)₀₋₁—S—(CH₂)₁₋₃—, —(CH₂)₀₋₁—N(R^(N))—(CH₂)₁₋₃—, and —(CH₂)₂₋₄—.

[0193] In a further particularly interesting embodiment, the present invention relates to an LNA of the general formula IIa

[0194] wherein X is —O—; B is selected from nucleobases, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands; R³ is a group Q*; each of Q and Q* is independently selected from hydrogen, azido, halogen, cyano, nitro, hydroxy, Prot-O—, Act-O—, mercapto, Prot-S—, Act-S—, C₁₋₆-alkylthio, amino, Prot-N(R^(H))—, Act-N(R^(H))—, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyl, optionally substituted C₂₋₆-alkynyloxy, monophosphate, diphosphate, triphosphate, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, ligands, carboxy, sulphono, hydroxymethyl, Prot-O—CH₂—, Act-O—CH₂—, aminomethyl, Prot-N(R^(H))—CH₂—, Act-N(R^(H))—CH₂—, carboxymethyl, sulphonomethyl, where Prot is a protection group for —OH, —SH, and —NH(R^(H)), respectively, Act is an activation group for —OH, —SH, and —NH(R^(H)), respectively, and R^(H) is selected from hydrogen and C₁₋₆-alkyl; R²* and R⁴* together designate a biradical selected from —O—, —S, —N(R*)—, —(CR*R*)_(r+s+1)—, —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, —(CR*R*)_(r)—N(R*)—(CR*R*)—, —O—(CR*R*)_(r+s)—O—, —S—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—S—, —N(R )—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—N(R*)—, —S—(CR*R*)_(r+s)—S—, —N(R*)—(CR*R*)_(r+s)—N(R*)—, —N(R*)—(CR*R*)_(r+s)—S—, and —S—(CR*R*)_(r+s)—N(R*)—; wherein each R* is independently selected from hydrogen, halogen, azido, cyano, nitro, hydroxy, mercapto, amino, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₆-alkoxy, optionally substituted C₁₋₆-alkyl, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and/or two adjacent (non-geminal) R* may together designate a double bond, and each of r and s is 0-3 with the proviso that the sum r+s is 1-4; each of the substituents R¹*, R², R³, R⁵, and R⁵* is independently selected from hydrogen, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, hydroxy, C₁₋₆-alkoxy, C₂₋₆-alkenyloxy, carboxy, C₁₋₆-alkoxycarbonyl, C₁₋₆-alkylcarbonyl, formyl, amino, mono- and di(C₁₋₆-alkyl)amino, carbamoyl, mono- and di(C₁₋₆-alkyl)-amino-carbonyl, C₁₋₆-alkyl-carbonylamino, carbamido, azido, C₁₋₆-alkanoyloxy, sulphono, sulphanyl, C₁₋₆-alkylthio, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and halogen, where two geminal substituents together may designate oxo; and basic salts and acid addition salts thereof; and with the proviso that any chemical group (including any nucleobase), which is reactive under the conditions prevailing in oligonucleotide synthesis, is optionally functional group protected. Preferably, one R* is selected from hydrogen, hydroxy, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and any remaining substituents R* are hydrogen. Especially, the biradical is selected from —O—, —(CH₂)₀₋₁—O—(CH₂)₁₋₃—, —(CH₂)₀₋₁—S—(CH₂)₁₋₃—, —(CH₂)₀₋₁—N(R^(N))—(CH₂)₁₋₃—, and —(CH₂)₂₋₄—.

[0195] Generally, the present invention provides oligomers having surprisingly good hybridisation properties with respect to affinity and specificity. Thus, the present invention provides an oligomer comprising at least one nucleoside analogue which imparts to the oligomer a T_(m) with a complementary DNA oligonucleotide which is at least 2.5° C. higher, preferably at least 3.5° C. higher, in particular at least 4.0° C. higher, especially at least 5.0° C. higher, than that of the corresponding unmodified reference oligonucleotide which does not comprise any nucleoside analogue. In particular, the T_(m) of the oligomer is at least 2.5×N° C. higher, preferably at least 3.5×N° C. higher, in particular at least 4.0×N° C. higher, especially at least 5.0×N° C. higher, where N is the number of nucleoside analogues.

[0196] In the case of hybridisation with a complementary RNA oligonucleotide, the at least one nucleoside analogue imparts to the oligomer a T_(m) with the complementary DNA oligonucleotide which is at least 4.0° C. higher, preferably at least 5.0° C. higher, in particular at least 6.0° C. higher, especially at least 7.0° C. higher, than that of the corresponding unmodified reference oligonucleotide which does not comprise any nucleoside analogue. In particular, the Tm of the oligomer is at least 4.0×N° C. higher, preferably at least 5.0×N° C. higher, in particular at least 6.0×N° C. higher, especially at least 7.0×N° C. higher, where N is the number of nucleoside analogues.

[0197] The term “corresponding unmodified reference oligonucleotide” is intended to mean an oligonucleotide solely consisting of naturally occurring nucleotides which represents the same nucleobases in the same absolute order (and the same orientation).

[0198] The T_(m) is measured under one of the following conditions (i.e. essentially as illustrated in Example 129):

[0199] a) 10 mM Na₂HPO₄, pH 7.0, 100 mM NaCl, 0.1 mM EDTA;

[0200] b) 10 mM Na₂HPO₄ pH 7.0, 0.1 mM EDTA; or

[0201] c) 3M tetrametylammoniumchlorid (TMAC), 10 mM Na₂HPO₄, pH 7.0, 0.1 mM EDTA;

[0202] preferably under conditions a), at equimolar amounts (typically 1.0 μM) of the oligomer and the complementary DNA oligonucleotide.

[0203] The oligomer is preferably as defined above, where the at least one nucleoside analogue has the formula I where B is a nucleobase. In particular interesting is the cases where at least one nucleoside analogue includes a nucleobase selected from adenine and guanine.

[0204] Furthermore, with respect to specificity and affinity, the oligomer, when hybridised with a partially complementary DNA oligonucleotide, or a partially complementary RNA oligonucleotide, having one or more mismatches with said oligomer, should exhibit a reduction in T_(m), as a result of said mismatches, which is equal to or greater than the reduction which would be observed with the corresponding unmodified reference oligonucleotide which does not comprise any nucleoside analogues. Also, the oligomer should have substantially the same sensitivity of T_(m) to the ionic strength of the hybridisation buffer as that of the corresponding unmodified reference oligonucleotide.

[0205] Oligomers defined herein are typically at least 30% modified, preferably at least 50% modified, in particular 70% modified, and in some interesting applications 100% modified.

[0206] The oligomers of the invention has substantially higher 3′-exonucleolytic stability than the corresponding unmodified reference oligonucleotide. This important property can be examined as described in Example 136.

[0207] Definitions

[0208] In the present context, the term “C₁₋₁₂-alkyl” means a linear, cyclic or branched hydrocarbon group having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, iso-propyl, cyclopropyl, butyl, tert-butyl, iso-butyl, cyclobutyl, pentyl, cyclopentyl, hexyl, cyclohexyl, and dodecyl. Analogously, the term “C₁₋₆-alkyl” means a linear, cyclic or branched hydrocarbon group having 1 to 6 carbon atoms, such as methyl, ethyl, propyl, iso-propyl, pentyl, cyclopentyl, hexyl, cyclohexyl, and the term “C₁₋₄-alkyl” is intended to cover linear, cyclic or branched hydrocarbon groups having 1 to 4 carbon atoms, e.g. methyl, ethyl, propyl, iso-propyl, cyclopropyl, butyl, iso-butyl, tert-butyl, cyclobutyl.

[0209] Preferred examples of “C₁₋₆-alkyl” are methyl, ethyl, propyl, iso-propyl, butyl, tert-butyl, iso-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, in particular methyl, ethyl, propyl, iso-propyl, tert-butyl, iso-butyl and cyclohexyl. Preferred examples of “C₁₋₄-alkyl” are methyl, ethyl, propyl, iso-propyl, butyl, tert-butyl, and iso-butyl.

[0210] Similarly, the term “C₂₋₁₂-alkenyl” covers linear, cyclic or branched hydrocarbon groups having 2 to 12 carbon atoms and comprising one unsaturated bond. Examples of alkenyl groups are vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, do-decaenyl. Analogously, the term “C₂₆-alkenyl” is intended to cover linear, cyclic or branched hydrocarbon groups having 2 to 6 carbon atoms and comprising one unsaturated bond. Preferred examples of alkenyl are vinyl, allyl, butenyl, especially allyl.

[0211] Similarly, the term “C₂₋₁₂-alkynyl” means a linear or branched hydrocarbon group having 2 to 12 carbon atoms and comprising a triple bond. Examples hereof are ethynyl, propynyl, butynyl, octynyl, and dodecanyl.

[0212] In the present context, i.e. in connection with the terms “alkyl”, “alkenyl”, and “alkynyl”, the term “optionally substituted” means that the group in question may be substituted one or several times, preferably 1-3 times, with group(s) selected from hydroxy (which when bound to an unsaturated carbon atom may be present in the tautomeric keto form), C₁₋₆-alkoxy (i.e. C₁₋₆-alkyl-oxy), C₂₋₆-alkenyloxy, carboxy, oxo (forming a keto or aldehyde functionality), C₁₋₆-alkoxycarbonyl, C₁₋₆-alkylcarbonyl, formyl, aryl, aryloxycarbonyl, aryloxy, arylcarbonyl, heteroaryl, heteroaryloxycarbonyl, heteroaryloxy, heteroarylcarbonyl, amino, mono- and di(C₁₋₆-alkyl)amino; carbamoyl, mono- and di(C₁₋₆-alkyl)aminocarbonyl, amino-C₁₋₆-alkyl-aminocarbonyl, mono- and di(C₁₋₆-alkyl)amino-C₁₋₆-alkyl-aminocarbonyl, C₁₋₆-alkylcarbonylamino, cyano, guanidino, carbamido, C₁₋₆-alkanoyloxy, sulphono, C₁₋₆-alkylsulphonyloxy, nitro, sulphanyl, C₁₋₆-alkylthio, halogen, where any aryl and heteroaryl may be substituted as specifically describe below for “optionally substituted aryl and heteroaryl”.

[0213] Preferably, the substituents are selected from hydroxy, C₁₋₆-alkoxy, carboxy, C₁₋₆, alkoxycarbonyl, C₁₋₆-alkylcarbonyl, formyl, aryl, aryloxycarbonyl, arylcarbonyl, heteroaryl, amino, mono- and di(C₁₋₆-alkyl)amino, carbamoyl, mono- and di(C₁₋₆-alkyl)-aminocarbonyl, amino-C₁₋₆-alkyl-aminocarbonyl, mono- and di(C₁₋₆-alkyl)amino-C₁₋₆-alkyl-aminocarbonyl, C₁₋₆-alkylcarbonylamino, cyano, carbamido, halogen, where aryl and heteroaryl may be substituted 1-5 times, preferably 1-3 times, with C₁₋₄-alkyl, C₁₋₄-alkoxy, nitro, cyano, amino or halogen. Especially preferred examples are hydroxy, C₁₋₆-alkoxy, carboxy, aryl, heteroaryl, amino, mono- and di(C₁₋₆-alkyl)amino, and halogen, where aryl and heteroaryl may be substituted 1-3 times with C₁₋₄-alkyl, C₁₋₄-alkoxy, nitro, cyano, amino or halogen.

[0214] In the present context the term “aryl” means a fully or partially aromatic carbocyclic ring or ring system, such as phenyl, naphthyl, 1,2,3,4-tetrahydronaphthyl, anthracyl, phenanthracyl, pyrenyl, benzopyrenyl, fluorenyl and xanthenyl, among which phenyl is a preferred example.

[0215] The term “heteroaryl” means a fully or partially aromatic carbocyclic ring or ring system where one or more of the carbon atoms have been replaced with heteroatoms, e.g. nitrogen (═N— or —NH), sulphur, and/or oxygen atoms. Examples of such heteroaryl groups are oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, pyrrolyl, imidazolyl, pyrazolyl, pyridinyl, pyrazinyl, pyridazinyl, piperidinyl, coumaryl, furyl, quinolyl, benzothiazolyl, benzotriazolyl, benzodiazolyl, benzooxozolyl, phthalazinyl, phthalanyl, triazolyl, tetrazolyl, isoquinolyl, acridinyl, carbazolyl, dibenzazepinyl, indolyl, benzopyrazolyl, phenoxazonyl.

[0216] In the present context, i.e. in connection with the terms “aryl” and “heteroaryl”, the term “optionally substituted” means that the group in question may be substituted one or several times, preferably 1-5 times, in particular 1-3 times) with group(s) selected from hydroxy (which when present in an enol system may be represented in the tautomeric keto form), C₁₋₆-alkyl, C₁₋₆-alkoxy, oxo (which may be represented in the tautomeric enol form), carboxy, C₁₋₆-alkoxycarbonyl, C₁₋₆-alkylcarbonyl, formyl, aryl, aryloxy, aryloxycarbonyl, arylcarbonyl, heteroaryl, amino, mono- and di(C₁₋₆-alkyl)amino; carbamoyl, mono- and di(C₁₋₆-alkyl)aminocarbonyl, amino-C₁₋₆-alkyl-aminocarbonyl, mono- and di(C₁₋₆-alkyl)amino-C₁₋₆-alkyl-aminocarbonyl, C₁₋₆-alkylcarbonylamino, cyano, guanidino, carbamido, C₁₋₆-alkanoyloxy, sulphono, C₁₋₆-alkylsulphonyloxy, nitro, sulphanyl, dihalogen-C₁₋₄-alkyl, trihalogen-C₁₋₄-alkyl, halogen, where aryl and heteroaryl representing substituents may be substituted 1-3 times with C₁₋₄-alkyl, C₁₋₄-alkoxy, nitro, cyano, amino or halogen. Preferred examples are hydroxy, C₁₋₆-alkyl, C₁₋₆-alkoxy, carboxy, C₁₋₆-alkoxycarbonyl, C₁₋₆-alkylcarbonyl, aryl, amino, mono- and di(C₁₋₆-alkyl)amino, and halogen, wherein aryl may be substituted 1-3 times with C₁₋₄-alkyl, C₁₋₄-alkoxy, nitro, cyano, amino or halogen.

[0217] “Halogen” includes fluoro, chloro, bromo, and iodo.

[0218] It should be understood that oligomers (wherein LNAs are incorporated) and LNAs as such include possible salts thereof, of which pharmaceutically acceptable salts are especially relevant. Salts include acid addition salts and basic salts. Examples of acid addition salts are hydrochloride salts, sodium salts, calcium salts, potassium salts, etc. Examples of basic salts are salts where the (remaining) counter ion is selected from alkali metals, such as sodium and potassium, alkaline earth metals, such as calcium, and ammonium ions (⁺N(R^(g))₃R^(h), where each of R^(g) and R^(h) independently designates optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, optionally substituted aryl, or optionally substituted heteroaryl). Pharmaceutically acceptable salts are, e.g., those described in Remington's Pharmaceutical Sciences, 17. Ed. Alfonso R. Gennaro (Ed.), Mack Publishing Company, Easton, Pa., U.S.A., 1985 and more recent editions and in Encyclopedia of Pharmaceutical Technology. Thus, the term “an acid addition salt or a basic salt thereof” used herein is intended to comprise such salts. Furthermore, the oligomers and LNAs as well as any intermediates or starting materials therefor may also be present in hydrate form.

[0219] Preparation of Monomers

[0220] In a preferred embodiment, nucleosides containing an additional 2′-O,4′-C-linked ring were synthesised by the following procedure:

[0221] Synthesis of a number of 4′-C-hydroxymethyl nucleosides have been reported earlier (R. D. Youssefyeh, J. P. H. Verheyden and J. G. Moffatt, J. Org. Chem., 1979, 44, 1301; G. H. Jones, M. Taniguchi, D. Tegg and J. G. Moffatt, J. Org. Chem., 1979, 44, 1309; C. O-Yang, H. Y. Wu, E. B. Fraser-Smith and K. A. M. Walker, Tetrahedron Lett., 1992, 33, 37; H. Thrane, J. Fensholdt, M. Regner and J. Wengel, Tetrahedron, 1995, 51, 10389; K. D. Nielsen, F. Kirpekar, P. Roepstorff and J. Wengel, Bioorg. Med. Chem., 1995, 3, 1493). For exemplification of synthesis of 2′-O,4′-C-linked bicyclic nucleosides we chose a strategy starting from 4′-C-hydroxymethyl furanose derivative 31. Benzylation, acetylation, and acetolysis followed by another acetylation afforded furanose 33, a key intermediate for nucleoside coupling. Stereoselective reaction with silylated thymine afforded compound 34 which was deacetylated to give nucleoside diol 35. Tosylation followed by base-induced ring closure afforded the 2′-O,4′-C-linked bicyclic nucleoside derivative 36. Debenzylation yielded the unprotected bicyclic nucleoside analogue 37 which was transformed into the 5′-O-4,4′-dimethoxytrityl protected analogue 38 and subsequently into the phosphoramidite derivative 39 for oligonucleotide synthesis. A similar procedure has been used for synthesis of the corresponding uracil, adenine, cytosine and guanine nucleosides as exemplified in the example section. This coupling method is only one of several possible as will be apparent for a person skilled in the art. A strategy starting from a preformed nucleoside is also possible. Thus, for example, conversion of uridine derivative 62 to derivative 44 was successfully accomplished by tosylation, deisopropylidination and base-induced ring-closure. As another example, conversion of nucleoside 67 into nucleoside 61B has been accomplished as depicted in FIG. 34. Conversion of the bicyclic thymine nucleoside 37 into the corresponding 5-methyl-cytosine nucleoside 65 was accomplished by a known reaction sequence using triazole and POCl₃ followed by benzoylation and treatment by ammonia. A similar procedure should be applicable for the synthesis of 57C from 44. As another example of possible strategies, coupling of precyclised furanose derivatives already containing an additional ring with nucleobase derivatives is possible. Such a strategy would in addition allow preparation of the corresponding α-nucleoside analogues. When coupling with a protected methyl furanoside of 4-C,2-O-methylene-D-ribofuranose, we obtained mainly a ring-opened product. However, coupling of 1-O-acetyl furanose 207 or thiophenyl furanose 212 yielded successfully LNA nucleosides with the α-anomers as one product. Incorporation of such α-LNA nucleosides will be possible using the standard oligomerisation techniques (as for the LNA oligomers containing Z) yielding α-LNA oligomers. In addition, a synthetic strategy performing nucleoside coupling using a 4′-C-hydroxymethyl furanose already activated for ring closure (e.g. by containing a mesyl or tosyl group at the 4′-C-hydroxymethyl group), is possible as exemplified by conversion of furanose 78 to nucleoside 79 followed by deprotection and ring closure to give 36. Chemical or enzymatic transglycosylation or anomerisation of appropriate furanose derivatives or nucleosides are yet other possible synthetic strategies. These and other related strategies allow for synthesis of bicyclic nucleosides containing other nucleobases or analogues thereof by either coupling with these nucleobases or analogues, or starting from preformed nucleoside derivatives.

[0222] The described examples are meant to be illustrative for the procedures and examples of this invention. The structures of the synthesised compounds were verified using 1 D or 2D NMR techniques, e.g. NOE experiments.

[0223] An additional embodiment of the present invention is to provide bicyclic nucleosides containing additional rings of different sizes and of different chemical structures. From the methods described it is obvious for a person skilled in the art of organic synthesis that cyclisation of other nucleosides is possible using similar procedures, also of nucleosides containing different C-branches. The person skilled in the art will be able to find inspiration and guidance for the preparation of substituted nucleoside analogue intermediates in the literature, see e.g. WO 96/14329. Regarding rings of different chemical compositions it is clear that using similar procedures or procedures well-established in the field of organic chemistry, synthesis of for example thio analogues of the exemplified oxo analogues is possible as is the synthesis of the corresponding amino analogues (using for example nucleophilic substitution reactions or reductive alkylations).

[0224] In the example section, synthesis of the amino LNA analogues 73-74F are described. Conversion of 74 and 74D into standard building blocks for oligomerisation was possible by 5′-O-DMT protection and 3′-O-phosphitylation following the standard procedures. For the amino LNA analogue, protection of the 2′-amino functionality is needed for controlled linear oligomerisation. Such protection can be accomplished using standard amino group protection techniques like, e.g., Fmoc, trifluoroacetyl or BOC. Alternatively, an N-alkyl group (e.g. benzyl, methyl, ethyl, propyl or functionalised alkyl) can be kept on during nucleoside transformations and oligomerisation. In FIGS. 35 and 36, strategies using N-trifluoroacetyl and N-methyl derivatives are shown. As outlined in FIG. 37, conversion of nucleoside 75 into the 2′-thio-LNA nucleoside analogue 76D has been successfully performed as has the subsequent syntheses of the phosphoramidite derivative 76F. Compound 76F has the required structure for automated synthesis of 2′-thio-LNA oligonucleotides. The N-trifluoroacetyl 2′-amino-LNA synthon 74A has the required structure for automated synthesis of 2′-amino-LNA oligonucleotides.

[0225] Synthesis of the corresponding cytosine, guanine, and adenine derivatives of the 2′-thio and 2′-amino LNA nucleosides can be accomplished using strategies analogous to those shown in FIGS. 35, 36 and 37. Alternative, the stereochemistry around C-2′ can be inverted before cyclisations either by using a conveniently configurated, e.g. an arabino-configurated, furanose synthon, or by inverting the configuration around the C-2′ carbon atom starting from a ribo-configurated nucleoside/furanose. Subsequent activation of the 2′-β-OH, e.g. by tosylation, double nucleophilic substitution as in the urasil/thymine example described above, could furnish the desired bicyclic 2′-thio-LNA or 2′-amino-LNA nucleosides. The thus obtained properly protected cytosine, guanine, and adenine analogues can be prepared for oligomerisation using the standard reactions (DMT-protection and phosphitylation) as described above for other examples.

[0226] Preparation of Oligomers

[0227] Linear-, branched- (M. Grøtli and B. S. Sproat, J. Chem. Soc., Chem. Commun., 1995, 495; R. H. E. Hudson and M. J. Damha, J. Am. Chem. Soc., 1993, 115, 2119; M. Von Büren, G. V. Petersen, K. Rasmussen, G. Brandenburg, J. Wengel and F. Kirpekar, Tetrahedron, 1995, 51, 8491) and circular- (G. Prakash and E. T. Kool, J. Am. Chem. Soc., 1992, 114, 3523) Oligo- and polynucleotides of the invention may be produced using the polymerisation techniques of nucleic acid chemistry well known to a person of ordinary skill in the art of organic chemistry. Phosphoramidite chemistry (S. L. Beaucage and R. P. Iyer, Tetrahedron, 1993, 49, 6123; S. L. Beaucage and R. P. Iyer, Tetrahedron, 1992, 48, 2223) was used, but e.g. H-phosphonate chemistry, phosphortriester chemistry or enzymatic synthesis could also be used. Generally, standard coupling conditions and the phosphoramidite approach was used, but for some monomers of the invention longer coupling time, and/or repeated couplings with fresh reagents, and/or use of more concentrated coupling reagents were used. As another possibility, activators more active than 1 H-tetrazole could also be used to increase the rate of the coupling reaction. The phosphoramidietes 39, 46, 53, 57D, 61D, and 66 all coupled with satisfactory >95% step-wise coupling yields. An all-phosphorothioate LNA oligomer (Table 7) was synthesised using standard procedures. Thus, by exchanging the normal, e.g. iodine/pyridine/H₂O, oxidation used for synthesis of phosphordiester oligomers with an oxidation using Beaucage's reagent (commercially available), the phosphorthioate LNA oligomer was efficiently synthesised (stepwise coupling yields >=98%). The 2′-amino-LNA and 2′methylamino-LNA oligonucleotides (Table 9) were efficiently synthesised (step-wise coupling yields ≧98%) using amidites 74A and 74F. The 2′-thio-LNA oligonucleotides (Table 8) were efficiently synthesised using amidite 76F using the standard phosphoramidite procedures as described above for LNA oligonucleotides. After synthesis of the desired sequence, work up was done using standard conditions (cleavage from solid support and removal of protection groups using 30% ammonia for 55° C. for 5 h). Purification of LNA oligonucleotides was done using disposable reversed phase purification cartridges and/or reversed phase HPLC and/or precipitation from ethanol or butanol. Capillary gel electrophoresis, reversed phase HPLC and MALDI-MS was used to verify the purity of the synthesised oligonucleotide analogues, and to verify that the desired number of bicyclic nucleoside analogues of the invention were incorporated as contemplated.

[0228] An additional aspect of the present invention is to furnish procedures for oligonucleotide analogues containing LNA linked by non-natural internucleoside linkages. For example, synthesis of the corresponding phosphorothioate or phosphoramidate analogues is possible using strategies well-established in the field of oligonucleotide chemistry (Protocols for Oligonucleotides and Analogs, vol 20, (Sudhir Agrawal, ed.), Humana Press, 1993, Totowa, N.J.; S. L. Beaucage and R. P. Iyer, Tetrahedron, 1993, 49, 6123; S. L. Beaucage and R. P. Iyer, Tetrahedron, 1992, 48, 2223; E. Uhlmann and A. Peyman, Chem. Rev., 90, 543).

[0229] Thus, generally the present invention also provides the use of an LNA as defined herein for the preparation of an LNA modified oligonucleotides. Is should be understood that LNA modified oligonucleotide may comprise normal nucleosides (i.e. naturally occurring nucleosides such as ribonucleosides and/or dioxyribonucleosides), as well as modified nucleosides different from those defined with the general formula II. In a particularly interesting embodiment, incorporation of LNA modulates the ability of the oligonucleotide to act as a substrate for nucleic acid active enzymes. Furthermore, solid support materials having immobilised thereto an optionally nucleobase protected and optionally 5′-OH protected LNA are especially interesting as material for the synthesis of LNA modified oligonucleotides where an LNA monomer is included in at the 3′ end. In this instance, the solid support material is preferable CPG, e.g. a readily (commercially) available CPG material onto which a 3′-functionalised, optionally nucleobase protected and optionally 5′-OH protected LNA is linked using the conditions stated by the supplier for that particular material. BioGenex Universial CPG Support (BioGenex, U.S.A.) can e.g. be used. The 5′-OH protecting group may, e.g., be a DMT group. 3′-functional group should be selected with due regard to the conditions applicable for the CPG material in question.

[0230] Applications

[0231] The present invention discloses the surprising finding that various novel derivatives of bicyclic nucleoside monomers (LNAs), when incorporated into oligonucleotides, dramatically increase the affinity of these modified oligonucleotides for both complementary ssDNA and ssRNA compared to the unmodified oligonucleotides. It further discloses the surprising finding that both fully and partly LNA modified oligonucleotides display greatly enhanced hybridisation properties for their complementary nucleic acid sequences. Depending on the application, the use of these LNAs thus offers the intriguing possibility to either greatly increase the affinity of a standard oligonucleotide without compromising specificity (constant size of oligonucleotide) or significantly increase the specificity without compromising affinity (reduction in the size of the oligonucleotide). The present invention also discloses the unexpected finding that LNA modified oligonucleotides, in addition to greatly enhanced hybridisation properties, display many of the useful physicochemical properties of normal DNA and RNA oligonucleotides. Examples given herein include excellent solubility, a response of LNA modified oligonucleotides to salts like sodium chloride and tetramethylammonium chloride which mimic that of the unmodified oligonucleotides, the ability of LNA modified oligonucleotides to act as primers for a variety of polymerases, the ability of LNA modified nucleotides to act as primers in a target amplification reaction using a thermostable DNA polymerase, the ability of LNA modified oligonucleotides to act as a substrate for T4 polynucleotide kinase, the ability of biotinylated LNAs to sequence specifically capture PCR amplicons onto a streptavidine coated solid surface, the ability of immobilised LNA modified oligonucleotides to sequence specifically capture amplicons and very importantly the ability of LNA modified oligonucleotides to sequence specifically target double-stranded DNA by strand invasion. Hence, it is apparent to one of ordinary skills in the art that these novel nucleoside analogues are extremely useful tools to improve the performance in general of oligonucleotide based techniques in therapeutics, diagnostics and molecular biology.

[0232] An object of the present invention is to provide monomeric LNAs according to the invention which can be incorporated into oligonucleotides using procedures and equipment well known to one skilled in the art of oligonucleotide synthesis.

[0233] Another object of the present invention is to provide fully or partly LNA modified oligonucleotides (oligomers) that are able to hybridise in a sequence specific manner to complementary oligonucleotides forming either duplexes or triplexes of substantially higher affinity than the corresponding complexes formed by unmodified oligonucleotides.

[0234] Another object of the present invention is to use LNAs to enhance the specificity of normal oligonucleotides without compromising affinity. This can be achieved by reducing the size (and therefore affinity) of the normal oligonucleotide to an extent that equals the gain in affinity resulting from the incorporation of LNAs.

[0235] Another object of the present invention is to provide fully or partly modified oligonucleotides containing both LNAs, normal nucleosides and other nucleoside analogues.

[0236] A further object of the present invention is to exploit the high affinity of LNAs to create modified oligonucleotides of extreme affinity that are capable of binding to their target sequences in a dsDNA molecule by way of “strand displacement”.

[0237] A further object of the invention is to provide different classes of LNAs which, when incorporated into oligonucleotides, differ in their affinity towards their complementary nucleosides. In accordance with the invention this can be achieved by either substituting the normal nucleobases G, A, T, C and U with derivatives having, for example, altered hydrogen bonding possibilities or by using LNAs that differ in their backbone structure. The availability of such different LNAs facilitates exquisite tuning of the affinity of modified oligonucleotides.

[0238] Another object of the present invention is to provide LNA modified oligonucleotides which are more resistant to nucleases than their unmodified counterparts.

[0239] Another object of the present invention is to provide LNA modified oligonucleotides which can recruit RNAseH.

[0240] An additional object of the present invention is to provide LNAs that can act as substrates for DNA and RNA polymerases thereby allowing the analogues to be either incorporated into a growing nucleic acid chain or to act as chain terminators.

[0241] A further object of the present invention is to provide LNAs that can act as therapeutic agents. Many examples of therapeutic nucleoside analogues are known and similar derivatives of the nucleoside analogues disclosed herein can be synthesised using the procedures known from the literature (E. De Clercq, J. Med. Chem. 1995, 38, 2491; P. Herdewijn and E. De Clercq: Classical Antiviral Agents and Design og New Antiviral Agents. In: A Textbook of Drug Design and Development; Eds. P. Krogsgaard-Larsen, T. Liljefors and U. Madsen; Harwood Academic Publishers, Amsterdam, 1996, p. 425; I. K. Larsen: Anticancer Agents.In: A Textbook of Drug Design and Development; Eds. P. Krogsgaard-Larsen, T. Liljefors and U. Madsen; Harwood Academic Publishers, Amsterdam, 1996, p. 460).

[0242] Double-stranded RNA has been demonstrated to posses anti-viral activity and tumour suppressing activity (Sharp et al., Eur. J. Biochem. 230(1): 97-103, 1995, Lengyel-P. et al., Proc. Natl. Acad. Sci. U.S.A., 90(13): 5893-5, 1993, and Laurent-Crawford et al., AIDS Res. Hum. Retroviruses, 8(2): 285-90, 1992). It is likely that double stranded LNAs may mimic the effect of therapeutically active double stranded RNAs and accordingly such double stranded LNAs has a potential as therapeutic drugs.

[0243] When used herein, the term “natural nucleic acid” refers to nucleic acids in the broadest sense, like for instance nucleic acids present in intact cells of any origin or vira or nucleic acids released from such sources by chemical or physical means or nucleic acids derived from such primary sources by way of amplification. The natural nucleic acid may be single, double or partly double stranded, and may be a relatively pure species or a mixture of different nucleic acids. It may also be a component of a crude biological sample containing other nucleic acids and other cellular components. On the other hand, the term “synthetic nucleic acids” refers to any nucleic acid produced by chemical synthesis.

[0244] The present invention also provides the use of LNA modified oligonucleotides in nucleic acid based therapeutic, diagnostics and molecular biology. The LNA modified oligonucleotides can be used in the detection, identification, capture, characterisation, quantification and fragmentation of natural or synthetic nucleic acids, and as blocking agents for translation and transcription in vivo and in vitro. In many cases it will be of interest to attach various molecules to LNA modified oligonucleotides. Such molecules may be attached to either end of the oligonucleotide or they may be attached at one or more internal positions. Alternatively, they may be attached to the oligonucleotide via spacers attached to the 5′ or 3′ end. Representative groups of such molecules are DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands. Generally all methods for labelling unmodified DNA and RNA oligonucleotides with these molecules can also be used to label LNA modified oligonucleotides. Likewise, all methods used for detecting labelled oligonucleotides generally apply to the corresponding labelled, LNA modified oligonucleotides.

[0245] Therapy

[0246] The term “strand displacement” relates to a process whereby an oligonucleotide binds to its complementary target sequence in a double stranded DNA or RNA so as to displace the other strand from said target strand.

[0247] In an aspect of the present invention, LNA modified oligonucleotides capable of performing “strand displacement” are exploited in the development of novel pharmaceutical drugs based on the “antigene” approach. In contrast to oligonucleotides capable of making triple helices, such “strand displacement” oligonucleotides allow any sequence in a dsDNA to be targeted and at physiological ionic strength and pH.

[0248] The “strand displacing” oligonucleotides can also be used advantageously in the antisense approach in cases where the RNA target sequence is inaccessible due to intramolecular hydrogen bonds. Such intramolecular structures may occur in mRNAs and can cause significant problems when attempting to “shut down” the translation of the mRNA by the antisense approach.

[0249] Other classes of cellular RNAs, like for instance tRNAs, rRNAs snRNAs and scRNAs, contain intramolecular structures that are important for their function. These classes of highly structured RNAs do not encode proteins but rather (in the form of RNA/protein particles) participate in a range of cellular functions such as mRNA splicing, polyadenylation, translation, editing, maintainance of chromosome end integrity, etc. Due to their high degree of structure, that impairs or even prevent normal oligonucleotides from hybridising efficiently, these classes of RNAs has so far not attracted interest as antisense targets.

[0250] The use of high affinity LNA monomers should facilitate the construction of antisense probes of sufficient thermostability to hybridise effectively to such target RNAs. Therefore, in a preferred embodiment, LNA is used to confer sufficient affinity to the oligonucleotide to allow it to hybridise to these RNA classes thereby modulating the qualitative and/or quantitative function of the particles in which the RNAs are found.

[0251] In some cases it may be advantageous to down-regulate the expression of a gene whereas in other cases it may be advantageous to activate it. As shown by Moøllegaard et al. (Møllegaard, N. E.; Buchardt, O.; Egholm, M.; Nielsen, P. E. Proc. Natl. Acad. Sci. U.S.A. 1994, 91, 3892), oligomers capable of “strand displacement” can function as RNA transcriptional activators. In an aspect of the present invention, the LNAs capable of “strand displacement” are used to activate genes of therapeutic interest.

[0252] In chemotherapy of numerous viral infections and cancers, nucleosides and nucleoside analogues have proven effective. LNA nucleosides are potentially useful as such nucleoside based drugs.

[0253] Various types of double-stranded RNAs inhibit the growth of several types of cancers. Duplexes involving one or more LNA oligonucleotide(s) are potentially useful as such double-stranded drugs.

[0254] The invention also concerns a pharmaceutical composition comprising a pharmaceutically active LNA modified oligonucleotide or a pharmaceutically active LNA monomer as defined above in combination with a pharmaceutically acceptable carrier.

[0255] Such compositions may be in a form adapted to oral, parenteral (intravenous, intraperitoneal), intramuscular, rectal, intranasal, dermal, vaginal, buccal, ocularly, or pulmonary administration, preferably in a form adapted to oral administration, and such compositions may be prepared in a manner well-known to the person skilled in the art, e.g. as generally described in “Remington's Pharmaceutical Sciences”, 17. Ed. Alfonso R. Gennaro (Ed.), Mark Publishing Company, Easton, Pa., U.S.A., 1985 and more recent editions and in the monographs in the “Drugs and the Pharmaceutical Sciences” series, Marcel Dekker.

[0256] Diagnostics

[0257] Several diagnostic and molecular biology procedures have been developed that utilise panels of different oligonucleotides to simultaneously analyse a target nucleic acid for the presence of a plethora of possible mutations. Typically, the oligonucleotide panels are immobilised in a predetermined pattern on a solid support such that the presence of a particular mutation in the target nucleic acid can be revealed by the position on the solid support where it hybridises. One important prerequisite for the successful use of panels of different oligonucleotides in the analysis of nucleic acids is that they are all specific for their particular target sequence under the single applied hybridisation condition. Since the affinity and specificity of standard oligonucleotides for their complementary target sequences depend heavily on their sequence and size this criteria has been difficult to fulfil so far.

[0258] In a preferred embodiment, therefore, LNAs are used as a means to increase affinity and/or specificity of the probes and as a means to equalise the affinity of different oligonucleotides for their complementary sequences. As disclosed herein such affinity modulation can be accomplished by, e.g., replacing selected nucleosides in the oligonucleotide with an LNA carrying a similar nucleobase. As further shown herein, different classes of LNAs exhibit different affinities for their complementary nucleosides. For instance, the 2-3 bridged LNA with the T-nucleobase exhibits less affinity for the A-nucleoside than the corresponding 2-4 bridged LNA. Hence, the use of different classes of LNAs offers an additional level for fine-tuning the affinity of a oligonucleotide.

[0259] In another preferred embodiment the high affinity and specificity of LNA modified oligonucleotides is exploited in the sequence specific capture and purification of natural or synthetic nucleic acids. In one aspect, the natural or synthetic nucleic acids are contacted with the LNA modified oligonucleotide immobilised on a solid surface. In this case hybridisation and capture occurs simultaneously. The captured nucleic acids may be, for instance, detected, characterised, quantified or amplified directly on the surface by a variety of methods well known in the art or it may be released from the surface, before such characterisation or amplification occurs, by subjecting the immobilised, modified oligonucleotide and captured nucleic acid to dehybridising conditions, such as for example heat or by using buffers of low ionic strength.

[0260] The solid support may be chosen from a wide range of polymer materials such as for instance CPG (controlled pore glass), polypropylene, polystyrene, polycarbonate or polyethylene and it may take a variety of forms such as for instance a tube, a microtiter plate, a stick, a bead, a filter, etc. The LNA modified oligonucleotide may be immobilised to the solid support via its 5′ or 3′ end (or via the terminus of linkers attached to the 5′ or 3′ end) by a variety of chemical or photochemical methods usually employed in the immobilisation of oligonucleotides or by non-covalent coupling such as for instance via binding of a biotinylated LNA modified oligonucleotide to immobilised streptavidin. One preferred method for immobilising LNA modified oligonucleotides on different solid supports is photochemical using a photochemically active anthraquinone covalently attached to the 5′ or 3′ end of the modified oligonucleotide (optionally via linkers) as described in (WO 96/31557). Thus, the present invention also provide a surface carrying an LNA modified oligonucleotide.

[0261] In another aspect the LNA modified oligonucleotide carries a ligand covalently attached to either the 5′ or 3′ end. In this case the LNA modified oligonucleotide is contacted with the natural or synthetic nucleic acids in solution whereafter the hybrids formed are captured onto a solid support carrying molecules that can specifically bind the ligand.

[0262] In still another aspect, LNA modified oligonucleotides capable of performing “strand displacement” are used in the capture of natural and synthetic nucleic acids without prior denaturation. Such modified oligonucleotides are particularly useful in cases where the target sequence is difficult or impossible to access by normal oligonucleotides due to the rapid formation of stable intramolecular structures. Examples of nucleic acids containing such structures are rRNA, tRNA, snRNA and scRNA.

[0263] In another preferred embodiment, LNA modified oligonucleotides designed with the purpose of high specificity are used as primers in the sequencing of nucleic acids and as primers in any of the several well known amplification reactions, such as the PCR reaction. As shown herein, the design of the LNA modified oligonucleotides determines whether it will sustain a exponential or linear target amplification. The products of the amplification reaction can be analysed by a variety of methods applicable to the analysis of amplification products generated with normal DNA primers. In the particular case where the LNA modified oligonucleotide primers are designed to sustain a linear amplification the resulting amplicons will carry single stranded ends that can be targeted by complementary probes without denaturation. Such ends could for instance be used to capture amplicons by other complementary LNA modified oligonucleotides attached to a solid surface.

[0264] In another aspect, LNA modified oligos capable of “strand displacement” are used as primers in either linear or exponential amplification reactions. The use of such oligos is expected to enhance overall amplicon yields by effectively competing with amplicon re-hybridisation in the later stages of the amplification reaction. Demers, et al. (Nucl. Acid Res. 1 995, Vol 23, 3050-3055) discloses the use of high-affinity, non-extendible oligos as a means of increasing the overall yield of a PCR reaction. It is believed that the oligomers elicit these effect by interfering with amplicon re-hybridisation in the later stages of the PCR reaction. It is expected that LNA modified oligos blocked at their 3′ end will provide the same advantage. Blocking of the 3′ end can be achieved in numerous ways like for instance by exchanging the 3′ hydroxyl group with hydrogen or phosphate. Such 3′ blocked LNA modified oligos can also be used to selectively amplify closely related nucleic acid sequences in a way similar to that described by Yu et al. (Biotechniques, 1997, 23, 714-71 6).

[0265] In recent years, novel classes of probes that can be used in for example real-time detection of amplicons generated by target amplification reactions have been invented. One such class of probes have been termed “Molecular Beacons”. These probes are synthesised as partly self-complementary oligonucleotides containing a fluorophor at one end and a quencher molecule at the other end. When free in solution the probe folds up into a hairpin structure (guided by the self-complimentary regions) which positions the quencher in sufficient closeness to the fluorophor to quench its fluorescent signal. Upon hybridisation to its target nucleic acid, the hairpin opens thereby separating the fluorophor and quencher and giving off a fluorescent signal.

[0266] Another class of probes have been termed “Taqman probes”. These probes also contain a fluorophor and a quencher molecule. Contrary to the Molecular Beacons, however, the quenchers ability to quench the fluorescent signal from the fluorophor is maintained after hybridisation of the probe to its target sequence. Instead, the fluorescent signal is generated after hybridisation by physical detachment of either the quencher or fluorophor from the probe by the action of the 5′ exonuxlease activity of a polymerase which has initiated synthesis from a primer located 5′ to the binding site of the Taqman probe.

[0267] High affinity for the target site is an important feature in both types of probes and consequently such probes tends to be fairly large (typically 30 to 40 mers). As a result, significant problems are encountered in the production of high quality probes. In a preferred embodiment, therefore, LNA is used to improve production and subsequent performance of Taqman probes and Molecular Beacons by reducing their size whilst retaining the required affinity.

[0268] In a further aspect, LNAs are used to construct new affinity pairs (either fully or partially modified oligonucleotides). The affinity constants can easily be adjusted over a wide range and a vast number of affinity pairs can be designed and synthesised. One part of the affinity pair can be attached to the molecule of interest (e.g. proteins, amplicons, enzymes, polysaccharides, antibodies, haptens, peptides, PNA, etc.) by standard methods, while the other part of the affinity pair can be attached to e.g. a solid support such as beads, membranes, micro-titer plates, sticks, tubes, etc. The solid support may be chosen from a wide range of polymer materials such as for instance polypropylene, polystyrene, polycarbonate or polyethylene. The affinity pairs may be used in selective isolation, purification, capture and detection of a diversity of the target molecules mentioned above.

[0269] The principle of capturing an LNA-tagged molecule by ways of interaction with another complementary LNA oligonucleotide (either fully or partially modified) can be used to create an infinite number of novel affinity pairs.

[0270] In another preferred embodiment the high affinity and specificity of LNA modified oligonucleotides are exploited in the construction of probes useful in in-situ hybridisation. For instance, LNA could be used to reduce the size of traditional DNA probes whilst maintaining the required affinity thereby increasing the kinetics of the probe and its ability to penetrate the sample specimen. The ability of LNA modified oligonucleotides to “strand invade” double stranded nucleic acid structures are also of considerable advantage in in-situ hybridisation, because it facilitates hybridisation without prior denaturation of the target DNA/RNA.

[0271] In another preferred embodiment, LNA modified oligonucleotides to be used in antisense therapeutics are designed with the dual purpose of high affinity and ability to recruit RNAseH. This can be achieved by, for instance, having LNA segments flanking an unmodified central DNA segment.

[0272] The present invention also provides a kit for the isolation, purification, amplification, detection, identification, quantification, or capture of natural or synthetic nucleic acids, where the kit comprises a reaction body and one or more LNA modified oligonucleotides (oligomer) as defined herein. The LNA modified oligonucleotides are preferably immobilised onto said reactions body.

[0273] The present invention also provides a kit for the isolation, purification, amplification, detection, identification, quantification, or capture of natural or synthetic nucleic acids, where the kit comprises a reaction body and one or more LNAs as defined herein. The LNAs are preferably immobilised onto said reactions body (e.g. by using the immobilising techniques described above).

[0274] For the kits according to the invention, the reaction body is preferably a solid support material, e.g. selected from borosilicate glass, soda-lime glass, polystyrene, polycarbonate, polypropylene, polyethylene, polyethyleneglycol terephthalate, polyvinylacetate, polyvinylpyrrolidinone, polymethylmethacrylate and polyvinylchloride, preferably polystyrene and polycarbonate. The reaction body may be in the form of a specimen tube, a vial, a slide, a sheet, a film, a bead, a pellet, a disc, a plate, a ring, a rod, a net, a filter, a tray, a microtitre plate, a stick, or a multi-bladed stick.

[0275] The kits are typically accompanied by a written instruction sheet stating the optimal conditions for use of the kit.

[0276] The above-mentioned diagnostic and therapeutic aspects of the present invention have been illustrated with the following examples. 

1. An oligomer (hereinafter termed “LNA modified oligonucleotide”) comprising at least one nucleoside analogue (hereinafter termed “LNA”) of the general formula I

wherein X is selected from —O—, —S—, —N(R^(N)*), —C(R⁶R⁶*)—, —O—C(R⁷R⁷*)—, —C(R⁶R⁶*)—O—, —S—C(R⁷R⁷*)—, —(R⁶R⁶*)—S—, —N(R^(N)*)—C(R⁷R⁷*)—, —C(R⁶R⁶*)—N(R^(N)*)—, and —C(R⁶R⁶*)—C(R⁷R⁷*)—; B is selected from hydrogen, hydroxy, optionally substituted C₁₋₄-alkoxy, optionally substituted C₁₋₄-alkyl, optionally substituted C₁₋₄-acyloxy, nucleobases, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands; P designates the radical position for an internucleoside linkage to a succeeding monomer, or a 5′-terminal group, such internucleoside linkage or 5′-terminal group optionally including the substituent R⁵; one of the substituents R², R²*, R³, and R³* is a group P* which designates an internucleoside linkage to a preceding monomer, or a 3′-terminal group; one or two pairs of non-geminal substituents selected from the present substituents of R¹*, R⁴*, R⁵, R⁵*, R⁶, R⁶*, R⁷, R⁷*, R^(N)*, and the ones of R², R²*, R³, and R³* not designating P* each designates a biradical consisting of 1-8 groups/atoms selected from —C(R^(a)R^(b))—, —C(R^(a))═C(R^(a))—, —C(R^(a))═N—, —O—, —Si(R^(a))₂—, —S—, —SO₂—, —N(R^(a))—, and >C═Z, wherein Z is selected from —O—, —S—, and —N(R^(a))—, and R^(a) and R^(b) each is independently selected from hydrogen, optionally substituted C₁₋₁₂-alkyl, optionally substituted C₂₋₁₂-alkenyl, optionally substituted C₂₋₁₂-alkynyl, hydroxy, C₁₋₁₂-alkoxy, C₂₋₁₂-alkenyloxy, carboxy, C₁₋₁₂-alkoxycarbonyl, C₁₋₁₂-alkylcarbonyl, formyl, aryl, aryloxy-carbonyl, aryloxy, arylcarbonyl, heteroaryl, heteroaryloxycarbonyl, heteroaryloxy, heteroarylcarbonyl, amino, mono- and di(C₁₋₆-alkyl)amino, carbamoyl, mono- and di(C₁₋₆-alkyl)-amino-carbonyl, amino-C₁₋₆-alkyl-aminocarbonyl, mono- and di(C₁₋₆-alkyl)amino-C₁₋₆-alkyl-aminocarbonyl, C₁₋₆-alkyl-carbonylamino, carbamido, C₁₋₆-alkanoyloxy, sulphono, C₁₋₆-alkylsulphonyloxy, nitro, azido, sulphanyl, C₁₋₆-alkylthio, halogen, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, where aryl and heteroaryl may be optionally substituted, and where two geminal substituents R^(a) and R^(b) together may designate optionally substituted methylene (═CH₂), and wherein two non-geminal or geminal substitutents selected from R^(a), R^(b), and any of the substituents R¹*, R², R²*, R³, R³*, R⁴*, R⁵, R⁵*, R⁶ and R⁶*, R⁷, and R⁷* which are present and not involved in P, P or the biradical(s) together may form an associated biradical selected from biradicals of the same kind as defined before; said pair(s) of non-geminal substituents thereby forming a mono- or bicyclic entity together with (i) the atoms to which said non-geminal substituents are bound and (ii) any intervening atoms; and each of the substituents R¹*, R², R²*, R³, R⁴*, R⁵, R⁵*, R⁶ and R⁶*, R⁷, and R⁷* which are present and not involved in P, P* or the biradical(s), is independently selected from hydrogen, optionally substituted C₁₋₁₂-alkyl, optionally substituted C₂₋₁₂-alkenyl, optionally substituted C₂₋₁₂-alkynyl, hydroxy, C₁₋₂-alkoxy, C₂₋₁₂-alkenyloxy, carboxy, C₁₋₁₂-alkoxycarbonyl, C₁₋₁₂-alkylcarbonyl, formyl, aryl, aryloxy-carbonyl, aryloxy, arylcarbonyl, heteroaryl, heteroaryloxy-carbonyl, heteroaryloxy, heteroarylcarbonyl, amino, mono- and di(C₁₋₆-alkyl)amino, carbamoyl, mono- and di(C₁₋₆-alkyl)-aminocarbonyl, amino-C₁₋₆-alkyl-aminocarbonyl, mono- and di(C₁₋₆-alkyl)amino-C₁₋₆-alkyl-aminocarbonyl, C₁₋₆-alkyl-carbonylamino, carbamido, C₁₋₆-alkanoyloxy, sulphono, C₁₋₆-alkylsulphonyloxy, nitro, azido, sulphanyl, C₁₋₆-alkylthio, halogen, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, where aryl and heteroaryl may be optionally substituted, and where two geminal substituents together may designate oxo, thioxo, imino, or optionally substituted methylene, or together may form a spiro biradical consisting of a 1-5 carbon atom(s) alkylene chain which is optionally interrupted and/or terminated by one or more heteroatoms/groups selected from —O—, —S—, and —(NR^(N))— where R^(N) is selected from hydrogen and C₁₋₄-alkyl, and where two adjacent (non-geminal) substituents may designate an additional bond resulting in a double bond; and R^(N)*, when present and not involved in a biradical, is selected from hydrogen and C₁₋₄-alkyl; and basic salts and acid addition salts thereof; with the proviso that, (i) R³ and R⁵ do not together designate a biradical selected from —CH₂—CH₂—, —O—CH₂—, when LNA is a bicyclic nucleoside analogue; (ii) R³, R⁵, and R⁵* do not together designate a triradical —CH₂—CH(−)—CH₂— when LNA is a tricyclic nucleoside analogue; (iii) R¹* and R⁶* do not together designate a biradical —CH₂— when LNA is a bicyclic nucleoside analogue; and (iv) R⁴* and R⁶* do not together designate a biradical —CH₂— when LNA is a bicyclic nucleoside analogue.
 2. An oligomer according to claim 1, wherein the one or two pairs of non-geminal substituents, constituting one or two biradical(s), respectively, are selected from the present substituents of R¹*, R⁴*, R⁶, R⁶*, R⁷, R⁷*, R^(N)*, and the ones of R², R²*, R³, and R³* not designating P*.
 3. An oligomer according to claim 1, comprising 1-10000 LNA(s) of the general formula I and 0-10000 nucleosides selected from naturally occurring nucleosides and nucleoside analogues, with the proviso that the sum of the number of nucleosides and the number of LNA(s) is at least
 2. 4. An oligomer according to claim 3, wherein at least one LNA comprises a nucleobase as the substituent B.
 5. An oligomer according to claim 1, wherein one of the substituents R³ and R³* designates P*.
 6. An oligomer according to claim 1, wherein the LNA(s) has/have the following formula 1a

wherein P, P*, B, X, R¹*, R², R²*, R³, R⁴*, R⁵, and R⁵* are as defined in claim
 1. 7. An oligomer according to claim 6, wherein R³ designates P*.
 8. An oligomer according to claim 1, comprising one biradical constituted by a pair of (two) non-geminal substituents.
 9. An oligomer according to claim 1, wherein X is selected from —(CR⁶R⁶*)—, —O—, —S—, and —N(R^(N)*).
 10. An oligomer according to claim 1, wherein the biradical(s) constituted by pair(s) of non-geminal substituents is/are selected from —(CR*R*)_(r)—Y—(CR*R*)_(s)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—Y—, —Y—(CR*R*)_(r+s)—Y—, —Y—(CR*R*)_(r)—Y—(CR*R*)_(s)—, —(CR*R*)_(r+s)—, —Y—, —Y—Y—, wherein each Y is independently selected from —O—, —S—, —Si(R*)₂—, —N(R*)—, >C═O, —C(═O)—N(R*)—, and —N(R*)—C(═O)—, each R* is independently selected from hydrogen, halogen, azido, cyano, nitro, hydroxy, mercapto, amino, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and/or two adjacent (non-geminal) R* may together designate a double bond, and each of r and s is 0-4 with the proviso that the sum r+s is 1-5.
 11. An oligomer according to claim 10, wherein each biradical is independently selected from —Y—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—, and —Y—(CR*R*)_(r+s)—Y—, wherein and each of r and s is 0-3 with the proviso that the sum r+s is 1-4.
 12. An oligomer according to claim 11, wherein i) R²* and R⁴* together designate a biradical selected from —Y—, —(CR*R*)_(r+s+1)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—, and —Y—(CR*R*)_(r+s)—Y—; (ii) R² and R³ together designate a biradical selected from —Y—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—, and —Y—(CR*R*)_(r+s)—Y—; (iii) R²* and R³ together designate a biradical selected from —Y—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—, and —Y—(CR*R*)_(r+s)—Y—; (iv) R³ and R⁴* together designate a biradical selected from —Y—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—, and —Y—(CR*R*)_(r+s)—Y—; (v) R³ and R⁵ together designate a biradical selected from —Y′—, —(CR*R*)_(r+s+1)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—, and —Y—(CR*R*)_(r+s)—Y—; (vi) R¹* and R⁴* together designate a biradical selected from —Y′—, —(CR*R*)_(r+s+1)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—, and —Y—(CR*R*)_(r+s)—NR*—; or (vii) R¹* and R²* together designate a biradical selected from —Y—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—Y—(CR*R*)_(s)—, and —Y—(CR*R*)_(r+s)—Y—; wherein each of r and s is 0-3 with the proviso that the sum r+s is 1-4, and where Y′ is selected from —NR*—C(═O)— and —C(═O)—NR*—.
 13. An oligomer according to claim 1 2, wherein one of the following criteria applies for at least one LNA: (i) R²* and R⁴* together designate a biradical selected from —O—, —S—, —N(R*)—, —(CR*R*)_(r+s+1)—, —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—, —O—(CR*R*)_(r+s)—O—, —S—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—S—, —N(R*)—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—N(R*)—, —S—(CR*R*)_(r+s)—S—, —N(R*)—(CR*R*)_(r+s)—N(R*)—, —N(R*)—(CR*R*)_(r+s)—S—, and —S—(CR*R*)_(r+s)—N(R*)—; (ii) R² and R³ together designate a biradical selected from —O—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—O—(CR*R*)_(r)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; (iii) R²* and R³ together designate a biradical selected from —O—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)— and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; (iv) R³ and R⁴* together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; (v) R³and R⁵ together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; or (vi) R¹ and R⁴* together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; (vii) R¹* and R²* together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; wherein each of r and s is 0-3 with the proviso that the sum r+s is 1-4, and where X is selected from —O—, —S—, and —N(R^(H))— where R^(H) designates hydrogen or C₁₋₄-alkyl.
 14. An oligomer according to claim 13, wherein R³* designates P*.
 15. An oligomer according to claim 14, wherein R²* and R⁴* together designate a biradical.
 16. An oligomer according to claim 15, wherein X is O, R² is selected from hydrogen, hydroxy, and optionally substituted C₁₋₆-alkoxy, and R¹*, R³, R⁵, and R⁵* designate hydrogen.
 17. An oligomer according to claim 1 6, wherein the biradical is selected from —O—, —(CH₂)₀₋₁-O-(CH₂)₁₋₃—, —(CH₂)₀₋₁—S—(CH₂)₁₋₃—, and —(CH₂)₀₋₁—N(R^(N))—(CH₂)₁₋₃—.
 18. An oligomer according to claim 17, wherein the biradical is selected from —O—CH₂—, —S—CH₂— and —N(R^(N))—CH₂—.
 19. An oligomer according to claim 15, wherein B is selected from nucleobases.
 20. An oligomer according to claim 19, wherein the oligomer comprises at least one LNA wherein B is selected from adenine and guanine and at least one LNA wherein B is selected from thymine, cytosine and urasil.
 21. An oligomer according to claim 1 6, wherein the biradical is —(CH₂)₂₋₄—.
 22. An oligomer according to claim 14, wherein R² and R³ together designate a biradical.
 23. An oligomer according to claim 22, wherein X is O, R²* is selected from hydrogen, hydroxy, and optionally substituted C₁₋₆-alkoxy, and R¹*, R⁴*, R⁵, and R⁵* designate hydrogen.
 24. An oligomer according to claim 23, wherein the biradical is —(CH₂)₀₋₁—O—(CH₂)₁₋₃—.
 25. An oligomer according to claim 23, wherein the biradical is —(CH₂)₁₋₄—.
 26. An oligomer according to claim 14, wherein one R* is selected from hydrogen, hydroxy, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and any remaining substituents R* are hydrogen.
 27. An oligomer according to claim 14, wherein a group R* in the biradical of at least one LNA is selected from DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands.
 28. An oligomer according to claim 14, wherein the LNA(s) has/have the general formula Ia.
 29. An oligomer according to claim 1 of the general formula la

wherein X is —O—; B is selected from nucleobases, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands; P designates the radical position for an internucleoside linkage to a succeeding monomer, or a 5′-terminal group, such internucleoside linkage or 5′-terminal group optionally including the substituent R⁵; R³ is a group P* which designates an internucleoside linkage to a preceding monomer, or a 3′-terminal group; R²* and R⁴* together designate a biradical selected from —O—, —S—, —N(R*)—, —(CR*R*)_(r+s+1)—, —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)—S—(CR*R*)_(s)—, —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—, —O—(CR*R*)_(r+s)—O—, —S—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—S—, —N(R*)—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—N(R*)—, —S—(CR*R*)_(r+s)—S—, —N(R*)—(CR*R*)_(r+s)—N(R*)—, —N(R*)—(CR*R*)_(r+s)—S— and —S—(CR*R*)_(r+s)—N(R*)—; wherein each R* is independently selected from hydrogen, halogen, azido, cyano, nitro, hydroxy, mercapto, amino, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and/or two adjacent (non-geminal) R* may together designate a double bond, and each of r and s is 0-3 with the proviso that the sum r+s is 1-4;each of the substituents R¹*, R², R³, R⁵, and R⁵* is independently selected from hydrogen, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, hydroxy, C₁₋₆-alkoxy, C₂₋₆-alkenyloxy, carboxy, C₁₋₆-alkoxycarbonyl, C₁₋₆-alkylcarbonyl, formyl, amino, mono- and di(C₁₋₆-alkyl)amino, carbamoyl, mono- and di(C₁₋₆-alkyl)-aminocarbonyl, C₁₋₆-alkyl-carbonylamino, carbamido, azido, C₁₋₆-alkanoyloxy, sulphono, sulphanyl, C₁₋₆-alkylthio, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and halogen, where two geminal substituents together may designate oxo; and basic salts and acid addition salts thereof.
 30. An oligomer according to claim 29, wherein one R* is selected from hydrogen, hydroxy, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and any remaining substituents R* are hydrogen.
 31. An oligomer according to claim 29, wherein the biradical is selected from —O—, —(CH₂)₀₋₁—O—(CH₂)₁₋₃—, —(CH₂)₀₋₁—S—(CH₂)₁₋₃—, —(CH₂)₀₋₁—N(R^(N))—(CH₂)₁₋₃—, and —(CH₂)₂₋₄—.
 32. An oligomer according to claim 31, wherein the biradical is selected from —O—CH₂—, —S—CH₂— and —N(R^(N))—CH₂—.
 33. An oligomer according to claim 29, wherein B is selected from nucleobases.
 34. An oligomer according to claim 33, wherein the oligomer comprises at least one LNA wherein B is selected from adenine and guanine and at least one LNA wherein B is selected from thymine, cytosine and urasil.
 35. An oligomer according to claim 29, wherein R² is selected from hydrogen, hydroxy and optionally substituted C₁₋₆-alkoxy, and R¹*, R³, R⁵, and R⁵* designate hydrogen.
 36. An oligomer according to claim 1, wherein any internucleoside linkage of the LNA(s) is selected from linkages consisting of 2 to 4 groups/atoms selected from —CH₂—, —O—, —S—, —NR^(H)—, >C═O, >C═NR^(H), >C═S, —Si(R″)₂——SO—, —S(O)₂—, —P(O)₂—, —P(O,S)—, —P(S)₂—, —PO(R″)—, —PO(OCH₃)—, and —PO(NHR^(H)), where R^(H) is selected form hydrogen and C₁₋₄-alkyl, and R″ is selected from C₁₋₆-alkyl and phenyl.
 37. An oligomer according to claim 36, wherein any internucleoside linkage of the LNA(s) is selected from —CH₂—CH₂—CH₂—, —CH₂—CO—CH₂—, —CH₂—CHOH—CH₂—, —O—CH₂—O—, —O—CH₂—CH₂—, —O—CH₂—CH═, —CH₂—CH₂—O—, —NR^(H)—CH₂—CH₂—, —CH₂—CH₂—NR^(H)—, CH₂NR^(H)—CH₂—, —O—CH₂—CH₂—NR^(H)—, —NR^(H)—CO—O—, —NR^(H)—CO—NR^(H)—, —NR^(H)CS—NR^(H), —NR^(H)—C(═NR^(H))—NR^(H)—, —NR^(H)—CO—CH₂—NR^(H)—, —O—CO—O—, —O—CO—CH₂—O—, —O—CH₂—CO—O—, —CH₂—CO—NR^(H), —O—CO—NR^(H)—, —NR^(H)CO—CH₂—, —O—CH₂—CO—NR^(H)—, —O—CH₂—CH₂—NR^(H)—, —CH═N—O—, —CH₂—NR^(H)—O—, —CH₂—O—N═, —CH₂—O—NR^(H)—, —CO—NR^(H)—CH₂—, —CH₂—NR^(H)—O—, —CH₂—NR^(H)—CO—, —O—NR^(H)—CH₂—, —O—NR^(H)—, —O—CH₂—S—, —S—CH₂—O—, —CH₂—CH₂—S—, —O—CH₂—CH₂—S—, —S—CH₂—CH═, —S—CH₂—CH₂—, —S—CH₂—CH₂—O—, —S—CH₂—CH₂—S—, —CH₂—S—CH₂—, —CH₂—SO—CH₂—, —CH₂—SO₂—CH₂—, —O—SO—O—, —O—S(O)₂—O—, —O—S(O)₂—CH₂—, —O—S(O)₂—NR^(H)—, —NR^(H)—S(O)₂—CH₂—, —O—S(O)₂—CH₂—, —O—P(O)₂—O—, —O—P(O,S)—O—, —O—P(S)₂—O—, —S—P(O)₂—O—, —S—P(O,S)—O—, —S—P(S)₂—O—, —O—P(O)₂—S—, —O—P(O,S)—S—, —O—P(S)₂—S—, —S—P(O)₂—S—, —S—P(O,S)—S—, —S—P(S)₂—S—, —O—PO(R″)—O—, —O—PO(OCH₃)—O—, —O—PO(BH₃)—O—, —O—PO(NHR^(N))—O—, —O—P(O)₂—NR^(H)—, —NR^(H)—P(O)₂—O—, —O—P(O,NR^(H))—O—, and —O—Si(R″)₂—O—.
 38. An oligomer according to claim 37, wherein any internucleoside linkage of the LNA(s) is selected from —CH₂—CO—NR^(H)—, —CH₂—NR^(H)—O—, —S—CH₂—O—, —O—P(O)₂—O—, —O—P(O,S)—O—, —O—P(S)₂—O—, NR^(H)P(O)₂—O—, —O—P(O,NR^(H))—O—, —O—PO(R″)—O—, —O—PO(CH₃)—O—, and —O—PO(NHR^(N))—O—, where R^(H) is selected form hydrogen and C₁₋₄-alkyl, and R″ is selected from C₁₋₆-alkyl and phenyl.
 39. An oligomer according to claim 1, wherein each of the substituents R¹*, R², R²*, R³, R³*, R⁴*, R⁵, R⁵*, R⁶, R⁶*, R⁷, and R⁷* of the LNA(s), which are present and not involved in P, P* or the biradical(s), is independently selected from hydrogen, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, hydroxy, C₁₋₆-alkoxy, C₂₋₆-alkenyloxy, carboxy, C₁₋₆-alkoxycarbonyl, C₁₋₆-alkylcarbonyl, formyl, amino, mono- and di(C₁₋₆-alkyl)amino, carbamoyl, mono- and di(C₁₋₆-alkyl)-amino-carbonyl, C₁₋₆-alkyl-carbonylamino, carbamido, azido, C₁₋₆-alkanoyloxy, sulphono, sulphanyl, C₁₋₆-alkylthio, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and halogen, where two geminal substituents together may designate oxo, and where R^(N)*, when present and not involved in a biradical, is selected from hydrogen and C₁₋₄-alkyl.
 40. An oligomer according to claim 1, wherein X is selected from —O—, —S—, and —NR^(N)*—, and each of the substituents R¹*, R², R²*, R³, R³*, R⁴*, R⁵, R⁵*, R⁶, R⁶*, R⁷, and R⁷* of the LNA(s), which are present and not involved in P, P* or the biradical(s), designate hydrogen.
 41. An oligomer according to claim 1, wherein P is a 5′-terminal group selected from hydrogen, hydroxy, optionally substituted C₁₋₆-alkyl, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₈-alkylcarbonyloxy, optionally substituted aryloxy, monophosphate, diphosphate, triphosphate, and —W—A′, wherein W is selected from —O—, —S—, and —N(R^(H)) where R^(H) is selected from hydrogen and C₁₋₆-alkyl, and where A′ is selected from DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands.
 42. An oligomer according to claim 1, wherein P* is a 3′-terminal group selected from hydrogen, hydroxy, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkylcarbonyloxy, optionally substituted aryloxy, and —W—A′, wherein W is selected from —O—, —S—, and —N(R^(H)) where R^(H) is selected from hydrogen and C₁₋₆-alkyl, and where A′ is selected from DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands.
 43. An oligomer according to claims 1, having the following formula V: G-[Nu-L]_(n(0))-{[LNA-L]_(m(q))-[Nu-L]_(n(q))}_(q)-G*  V wherein q is 1-50; each of n(0), . . . , n(q) is independently 0-10000; each of m(1), . . . , m(q) is independently 1-10000; with the proviso that the sum of n(0), . . . , n(q) and m(1), . . . , m(q) is 2-15000; G designates a 5′-terminal group; each Nu independently designates a nucleoside selected from naturally occurring nucleosides and nucleoside analogues; each LNA independently designates a nucleoside analogue; each L independently designates an internucleoside linkage between two groups selected from Nu and LNA, or L together with G* designates a 3′-terminal group; and each LNA-L independently designates a nucleoside analogue of the general formula I:

wherein the substituents B, P, P*, R¹, R², R²*, R³, R⁴*, R⁵, and R⁵*, and X are as defined in claim
 1. 44. An oligomer according to claim 1, further comprising a PNA mono- or oligomer segment of the formula

wherein B is a defined above for the formula I, AASC designates hydrogen or an amino acid side chain, t is 1-5, and w is 1-50.
 45. An oligomer according to claim 1, which has an increased specificity towards complementary ssRNA or ssDNA compared to the native oligonucleotide.
 46. An oligomer according to claim 1, which has an increased affinity towards complementary ssRNA or ssDNA compared to the native oligonucleotide.
 47. An oligomer according to claim 1, which is capable of binding to a target sequence in a dsDNA or dsRNA molecule by way of “strand displacement” or by triple helix formation.
 48. An oligomer according to claim 1, which is more resistant to nucleases than the native oligonucleotide.
 49. An oligomer according to claim 1, which has nucleic acid catalytic activity (LNA modified ribozymes).
 50. An oligomer comprising at least one nucleoside analogue which imparts to the oligomer a T_(m) with a complementary DNA oligonucleotide which is at least 2.5° C. higher than that of the corresponding unmodified reference oligonucleotide which does not comprise any nucleoside analogue.
 51. An oligomer according to claim 50, wherein the T_(m) is at least 2.5×N° C. higher, where N is the number of nucleoside analogues.
 52. An oligomer comprising at least one nucleoside analogue which imparts to the oligomer a T_(m) with a complementary RNA oligonucleotide which is at least 4.0° C. higher than that of the corresponding unmodified reference oligonucleotide which does not comprise any nucleoside analogue.
 53. An oligomer according to claim 52, wherein the T_(m) is at least 4.0×N° C. higher, where N is the number of nucleoside analogues.
 54. An oligomer according to claim 50 or 52, wherein the oligomer is as defined in claim 1, where the at least one nucleoside analogue has the formula I where B is a nucleobase.
 55. An oligomer according to claim 50, wherein said oligomer, when hybridised with a partially complementary DNA oligonucleotide having one or more mismatches with said oligomer, exhibits a reduction in T_(m), as a result of said mismatches, which is equal to or greater than the reduction which would be observed with the corresponding unmodified reference oligonucleotide which does not comprise any nucleoside analogues.
 56. An oligomer according to claim 52, wherein said oligomer, when hybridised with a partially complementary RNA oligonucleotide having one or more mismatches with said oligomer, exhibits a reduction in T_(m), as a result of said mismatches, which is equal to or greater than the reduction which would be observed with the corresponding unmodified reference oligonucleotide which does not comprise any nucleoside analogues.
 57. An oligomer according to claim 50 or 52, which has substantially the same sensitivity of T_(m) to the ionic strength of the hybridisation buffer as that of the corresponding unmodified reference oligonucleotide.
 58. An oligomer according to claim 50 or 52, which is at least 30% modified.
 59. An oligomer according to claim 50 or 52, which has substantially higher 3′-exonucleolytic stability than the corresponding unmodified reference oligonucleotide.
 60. A nucleoside analogue (hereinafter LNA) of the general formula II

wherein the substituent B is selected from nucleobases, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands; X is selected from —O—, —S—, —N(R^(N)*)—, and —C(R⁶R⁶*)—; one of the substituents R², R²*, R³, and R³* is a group Q*; each of Q and Q* is independently selected from hydrogen, azido, halogen, cyano, nitro, hydroxy, Prot-O—, Act-O—, mercapto, Prot-S—, Act-S—, C₁₋₆-alkylthio, amino, Prot-N(R^(H)), Act-N(R^(H)), mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyl, optionally substituted C₂₋₆-alkynyloxy, monophosphate, diphosphate, triphosphate, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, ligands, carboxy, sulphono, hydroxymethyl, Prot-O-CH₂-, Act-O—CH₂—, aminomethyl, Prot-N(R^(H))—CH₂—, Act-N(R^(H))—CH₂—, carboxymethyl, sulphonomethyl, where Prot is a protection group for —OH, —SH, and —NH(R^(H)), respectively, Act is an activation group for —OH, —SH, and —NH(R^(H)), respectively, and R^(H) is selected from hydrogen and C₁₋₆-alkyl; (i) R²* and R⁴* together designate a biradical selected from —O—, —(CR*R*)_(r+s+1)—, —(CR*R*)_(r)—O—(CR*R*)_(s)—,—(CR*R*)_(r)—S—(CR*R*)_(s)—, —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—,—O—(CR*R*)_(r+s)—O—, —S—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—S—, —N(R*)—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—N(R*)—, —S—(CR*R*)_(r+s)—S—, —N(R*)—(CR*R*)_(r+s)—N(R*)—, —N(R*)—(CR*R*)_(r+s)—S—, and —S—(CR*R*)_(r+s)—N(R*)—; (ii) R² and R³ together designate a biradical selected from —O—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; (iii) R²* and R³ together designate a biradical selected from —O—, —(CR*R*)_(r+s)—, —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; (iv) R³ and R⁴* together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; (v) R³ and R⁵ together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(r)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; or (vi) R¹* and R⁴* together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; (vii) R¹* and R²* together designate a biradical selected from —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, and —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—; wherein each R* is independently selected from hydrogen, halogen, azido, cyano, nitro, hydroxy, mercapto, amino, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and/or two adjacent (non-geminal) R* may together designate a double bond, and each of r and s is 0-3 with the proviso that the sum r+s is 1-4; each of the substituents R¹*, R², R²*, R³, R⁴*, R⁵, and R⁵*, which are not involved in Q, Q* or the biradical, is independently selected from hydrogen, optionally substituted C₁₋₁₂-alkyl, optionally substituted C₂₋₁₂-alkenyl, optionally substituted C₂₋₁₂-alkynyl, hydroxy, C₁₋₁₂-alkoxy, C₂₋₁₂-alkenyloxy, carboxy, C₁₋₁₂-alkoxycarbonyl, C₁₋₁₂-alkylcarbonyl, formyl, aryl, aryloxy-carbonyl, aryloxy, arylcarbonyl, heteroaryl, hetero-aryloxy-carbonyl, heteroaryloxy, heteroarylcarbonyl, amino, mono- and di(C₁₋₆-alkyl)amino, carbamoyl, mono- and di(C₁₋₆-alkyl)-amino-carbonyl, amino-C₁₋₆-alkyl-aminocarbonyl, mono- and di(C₁₋₆-alkyl)amino-C₁₋₆-alkyl-aminocarbonyl, C₁₋₆-alkyl-carbonylamino, carbamido, C₁₋₆-alkanoyloxy, sulphono, C₁₋₆-alkylsulphonyloxy, nitro, azido, sulphanyl, C₁₋₆-alkylthio, halogen, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, where aryl and heteroaryl may be optionally substituted, and where two geminal substituents together may designate oxo, thioxo, imino, or optionally substituted methylene, or together may form a spiro biradical consisting of a 1-5 carbon atom(s) alkylene chain which is optionally interrupted and/or terminated by one or more heteroatoms/groups selected from —O—, —S—, and —(NR^(N))— where R^(N) is selected from hydrogen and C₁₋₄-alkyl, and where two adjacent (non-geminal) substituents may designate an additional bond resulting in a double bond; and R^(N)*, when present and not involved in a biradical, is selected from hydrogen and C₁₋₄-alkyl; and basic salts and acid addition salts thereof; with the first proviso that, (i) R³ and R⁵ do not together designate a biradical selected from —CH₂—CH₂—, —O—CH₂—, and —O—Si(^(i)Pr)₂—O—Si(^(i)Pr)₂—O—; and with the second proviso that any chemical group (including any nucleobase), which is reactive under the conditions prevailing in oligonucleotide synthesis, is optionally functional group protected.
 61. A nucleoside analogue according to claim 60, wherein the group B is selected from nucleobases and functional group protected nucleobases.
 62. A nucleoside analogue according to claim 60, wherein X is selected from —O—, —S—, and —N(R^(N)*)—.
 63. A nucleoside analogue according to claim 60, wherein each of the substituents R¹*, R², R²*, R³, R³*, R⁴*, R⁵, and R⁵*, which are present and not involved in Q, Q* or the biradical, is independently selected from hydrogen, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, hydroxy, C₁₋₆-alkoxy, C₂₋₆-alkenyloxy, carboxy, C₁₋₆-alkoxycarbonyl, C₁₋₆-alkylcarbonyl, formyl, amino, mono- and di(C₁₋₆-alkyl)amino, carbamoyl, mono- and di(C₁₋₆-alkyl)-amino-carbonyl, C₁₋₆-alkyl-carbonylamino, carbamido, azido, C₁₋₆-alkanoyloxy, sulphono, sulphanyl, C₁₋₆-alkylthio, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, ligands, and halogen, where two geminal substituents together may designate oxo, and where R^(N)*, when present and not involved in a biradical, is selected from hydrogen and C₁₋₄-alkyl, with the proviso that any hydroxy, amino, mono(C₁₋₆-alkyl)amino, sulfanyl, and carboxy is optionally protected.
 64. A nucleotide analogue according to claim 60, each of the substituents R¹*, R², R²*, R³, R³*, R⁴*, and R⁵, R⁵*, R⁶, R⁶*, which are present and not involved in Q* or the biradical, designate hydrogen.
 65. A nucleoside analogue according to claim 60, wherein R³* designates P*.
 66. A nucleoside analogue according to claims 60, wherein Q is independently selected from hydrogen, azido, halogen, cyano, nitro, hydroxy, Prot-O—, mercapto, Prot-S—, C₁₋₆-alkylthio, amino, Prot-N(R^(H)), mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyl, optionally substituted C₂₋₆-alkynyloxy, monophosphate, diphosphate, triphosphate, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, ligands, carboxy, sulphono, hydroxymethyl, Prot-O—CH₂—, aminomethyl, Prot-N(R^(H))—CH₂—, carboxymethyl, sulphonomethyl, where Prot is a protection group for —OH, —SH, and —NH(R^(H)), respectively, and R^(H) is selected from hydrogen and C₁₋₆-alkyl; and Q* is selected from hydrogen, azido, halogen, cyano, nitro, hydroxy, Act-O—, mercapto, Act-S—, C₁₋₆-alkylthio, amino, Act-N(R^(H))—, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyl, optionally substituted C₂₋₆-alkynyloxy, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, ligands, carboxy, sulphono, where Act is an activation group for —OH, —SH, and —NH(R^(H)), respectively, and R^(H) is selected from hydrogen and C₁₋₆-alkyl.
 67. A nucleotide analogue according to claim 60, having the general formula IIa

wherein the substituents Q, B, R¹*, R², R²*, R³, R³*, R⁴, R⁵, and R⁵* are as defined in claims
 60. 68. A nucleoside analogue according to claim 67, wherein R³ designates P*.
 69. A nucleoside analogue according to claim 68, wherein R² and R⁴* together designate a biradical.
 70. A nucleoside analogue according to claim 69, wherein X is O, R² selected from hydrogen, hydroxy, and optionally substituted C₁₋₆-alkoxy, and R¹*, R³, R⁵, and R⁵* designate hydrogen.
 71. A nucleoside analogue according to claim 70, wherein the biradical is selected from —O—, —(CH₂)₀₋₁—O—(CH₂)₁₋₃—, —(CH₂)₀₋₁—S—(CH₂)₁₋₃—, and —(CH₂)₀₋₁—N(R^(N))—(CH₂)₁₋₃—.
 72. A nucleoside analogue according to claim 71, wherein the biradical is selected from —O—CH₂—, —S—CH₂— and —N(R^(N))—CH₂—.
 73. A nucleoside analogue according to claim 69, wherein B is selected from nucleobases.
 74. A nucleoside analogue according to claim 73, wherein the oligomer comprises at least one LNA wherein B is selected from adenine and guanine and at least one LNA wherein B is selected from thymine, cytosine and urasil.
 75. A nucleoside analogue according to claim 70, wherein the biradical is —(CH₂)₂₋₄—.
 76. A nucleoside analogue according to claim 68, wherein R² and R³ together designate a biradical.
 77. A nucleoside analogue according to claim 76, wherein X is O, R²* is selected from hydrogen, hydroxy, and optionally substituted C₁₋₆-alkoxy, and R¹*, R⁴*, R⁵, and R⁵* designate hydrogen.
 78. A nucleoside analogue according to claim 77, wherein the biradical is —(CH₂)₀₋₁—O—(CH₂)₁₋₃—.
 79. A nucleoside analogue according to claim 77, wherein the biradical is —(CH₂)₁₋₄—.
 80. A nucleoside analogue according to claim 68, wherein one R* is selected from hydrogen, hydroxy, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and any remaining substituents R are hydrogen.
 81. A nucleoside analogue according to claim 68, wherein a group R* in the biradical of at least one LNA is selected from DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands.
 82. A nucleoside analogue according to claim 68, wherein the LNA(s) has/have the general formula Ia.
 83. A nucleoside analogue according to claim 60 of the general formula IIa

wherein X is —O—; B is selected from nucleobases, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands; R³ is a group Q*; each of Q and Q* is independently selected from hydrogen, azido, halogen, cyano, nitro, hydroxy, Prot-O—, Act-O—, mercapto, Prot-S—, Act-S—, C₁₋₆-alkylthio, amino, Prot-N(R^(H))—, Act-N(R^(H))—, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyl, optionally substituted C₂₋₆-alkynyloxy, monophosphate, diphosphate, triphosphate, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, ligands, carboxy, sulphono, hydroxymethyl, Prot-O—CH₂—, Act-O—CH₂—, aminomethyl, Prot-N(R^(H))—CH₂—, Act-N(R^(H))—CH₂—, carboxymethyl, sulphonomethyl, where Prot is a protection group for —OH, —SH, and —NH(R^(H)), respectively, Act is an activation group for —OH, —SH, and —NH(R^(H)), respectively, and R^(H) is selected from hydrogen and C₁₋₆-alkyl; R² and R⁴ together designate a biradical selected from —O—, —S, —N(R*)—, —(CR*R*)_(r+s+1)—, —(CR*R*)_(r)—O—(CR*R*)_(s)—, —(CR*R*)_(r)—S—(CR*R*)_(s)—, —(CR*R*)_(r)—N(R*)—(CR*R*)_(s)—, —O—(CR*R*)_(r+s)—O—, —S—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—S—, —N(R*)—(CR*R*)_(r+s)—O—, —O—(CR*R*)_(r+s)—N(R*)—, —S—(CR*R*)_(r+s)—S—, —N(R*)—(CR*R*)_(r+s)—N(R*)—, —N(R*)—(CR*R*)_(r+s)—S—, and —S—(CR*R*)_(r+s)—N(R*)—; wherein each R* is independently selected from hydrogen, halogen, azido, cyano, nitro, hydroxy, mercapto, amino, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and/or two adjacent (non-geminal) R* may together designate a double bond, and each of r and s is 0-3 with the proviso that the sum r+s is 1-4; each of the substituents R¹*, R², R³, R⁵, and R⁵* is independently selected from hydrogen, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, hydroxy, C₁₋₆-alkoxy, C₂₋₆-alkenyloxy, carboxy, C₁₋₆-alkoxycarbonyl, C₁₋₆-alkylcarbonyl, formyl, amino, mono- and di(C₁₋₆-alkyl)amino, carbamoyl, mono- and di(C₁₋₆-alkyl)-aminocarbonyl, C₁₋₆-alkyl-carbonylamino, carbamido, azido, C₁₋₆-alkanoyloxy, sulphono, sulphanyl, C₁₋₆-alkylthio, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and halogen, where two geminal substituents together may designate oxo; and basic salts and acid addition salts thereof; and with the proviso that any chemical group (including any nucleobase), which is reactive under the conditions prevailing in oligonucleotide synthesis, is optionally functional group protected.
 84. A nucleotide analogue according to claim 83, wherein one R* is selected from hydrogen, hydroxy, optionally substituted C₁₋₈-alkoxy, optionally substituted C₁₋₆-alkyl, DNA intercalators, photochemically active groups, thermochemically active groups, chelating groups, reporter groups, and ligands, and any remaining substituents R are hydrogen.
 85. A nucleotide analogue according to claim 83, wherein the biradical is selected from —O—, —(CH₂)₀₋₁—O—(CH₂)₁₋₃—, —(CH₂)₀₋₁—S—(CH₂)₁₋₃—, —(CH₂)₀₋₁—N(R^(N))—(CH₂)₁₋₃—, and —(CH₂)₂₋₄—.
 86. A nucleoside analogue according to claim 85, wherein the biradical is selected from —O—CH₂—, —S—CH₂— and —N(R^(N))—CH₂—.
 87. A nucleoside analogue according to claim 83, wherein B is selected from nucleobases.
 88. A nucleoside analogue according to claim 87, wherein the oligomer comprises at least one LNA wherein B is selected from adenine and guanine and at least one LNA wherein B is selected from thymine, cytosine and urasil.
 89. A nucleoside analogue according to claim 83, wherein B designates a nucleobase, X is —O—, R²* and R⁴* together designate a biradical selected from —(CH₂)₀₋₁—O—(CH₂)₁₋₃—, —(CH₂)₀₋₁—S—(CH₂)₁₋₃—, and —(CH₂)₀₋₁—N(R^(N))—(CH₂)₁₋₃— where R^(N) is selected from hydrogen and C₁₋₄-alkyl, Q designates Prot-O—, R³* is Q* which designates Act-OH, and R¹*, R², R³, R⁵, and R⁵* each designate hydrogen, wherein Act and Prot are as defined in claim
 58. 90. A nucleoside analogue according to claim 83, wherein B designates a nucleobase, X is —O—, R²* and R⁴* together designate a biradical selected from —(CH₂)₀₋₁—O—(CH₂)₁₋₃—, —(CH₂)₀₋₁—S—(CH₂)₁₋₃—, and —(CH₂)₀₋₁—N(R^(N))—(CH₂)₁₋₃— where R^(N) is selected from hydrogen and C₁₋₄-alkyl, Q is selected from hydroxy, mercapto, C₁₋₆-alkylthio, amino, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyloxy, monophosphate, diphosphate, and triphosphate, R³* is Q which is selected from hydrogen, azido, halogen, cyano, nitro, hydroxy, mercapto, C₁₋₆-alkylthio, amino, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyl, and optionally substituted C₂₋₆-alkynyloxy, R³ is selected from hydrogen, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, and optionally substituted C₂₋₆-alkynyl, and R¹*, R², R⁵, and R⁵* each designate hydrogen.
 91. A nucleoside analogue according to claim 83, wherein B designates a nucleobase, X is —O—, R² and R³ together designate a biradical selected from —(CH₂)₀₋₁—O—CH═CH—, —(CH₂)₀₋₁—S—CH═CH—, and —(CH₂)₀₋₁—N(R^(N))—CH═CH— where R^(N) is selected from hydrogen and C₁₋₄-alkyl, Q is selected from hydroxy, mercapto, C₁₋₆-alkylthio, amino, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyloxy, monophosphate, diphosphate, and triphosphate, R³* is Q* which is selected from hydrogen, azido, halogen, cyano, nitro, hydroxy, mercapto, C₁₋₆-alkylthio, amino, mono- or di(C₁₋₆-alkyl)amino, optionally substituted C₁₋₆-alkoxy, optionally substituted C₁₋₆-alkyl, optionally substituted C₂₋₆-alkenyl, optionally substituted C₂₋₆-alkenyloxy, optionally substituted C₂₋₆-alkynyl, and optionally substituted C₂₋₆-alkynyloxy, and R¹*, R²*, R⁴*, R⁵, and R⁵* each designate hydrogen.
 92. A nucleoside analogue according to claim 60, which is selected from (1R,3R,4R,7S)-7-(2-cyanoethoxy(diisopropylamino)phosphinoxy)-1-(4,4′-dimethoxytrityloxymethyl)-3-(thymin-1-yl)-2,5-dioxabicyclo[2.2.1]heptane, (1R,3R,4R,7S)-7-hydroxy-1-(4,4′-dimethoxytrityloxymethyl)-3-(thymin-1-yl)-2,5-dioxabicyclo[2.2.1]heptane-7-O-(2-chlorophenylphosphate), and (1R,3R,4R,7S)-7-hydroxy-1-(4,4′-dimethoxytrityloxymethyl)-3-(thymin-1-yl)-2,5-dioxabicyclo[2.2.1]heptane-7-O-(H-phosphonate) and the 3-(cytosin-1-yl), 3-(urasil-1-yl), 3-(adenin-1-yl) and 3-(guanin-1-yl) analogues thereof
 93. A method of using an LNA as defined in claim 60 for the preparation of an LNA modified oligonucleotide (an oligomer) as defined in claim
 1. 94. A method according to claim 93, wherein the LNA modified oligonucleotide comprises normal nucleosides as well as modified nucleosides different from those defined in claim
 60. 95. A method according to claim 93, wherein the incorporation of LNA modulates the ability of the oligonucleotide to act as a substrate for nucleic acid active enzymes.
 96. A method of using of an LNA as defined in claim 60 for the preparation of a conjugate of an LNA modified oligonucleotide and a compound selected from proteins, amplicons, enzymes, polysaccharides, antibodies, haptens, peptides, and PNA.
 97. A conjugate of an LNA modified oligonucleotide (an oligomer) as defined in claim 1 and a compound selected from proteins, amplicons, enzymes, polysaccharides, antibodies, haptens, peptides, and PNA.
 98. A method of using an LNA as defined in claim 60 as a substrate for enzymes active on nucleic acids.
 99. A method according to claim 98, wherein the substituent Q in the formula I in claim 60 designates a triphosphate,
 100. A method according to claim 98, wherein the LNA is used as a substrate for DNA and RNA polymerases.
 101. A method of using an LNA as defined in claim 60 as a therapeutic agent.
 102. A method of using an LNA as defined in claim 60 for diagnostic purposes.
 103. A solid support material having immobilised thereto an optionally nucleobase protected and optionally 5′-OH protected LNA.
 104. A method of using one or more LNA as defined in claim 60 in the construction of solid surface onto which LNA modified oligonucleotides of different sequences are attached.
 105. A method according to claim 113, wherein the LNA modified oligonucleotides are attached in a predetermined pattern.
 106. A method according to claim 113, wherein the LNAs are used to equalise the T_(m) of the corresponding unmodified reference oligonucleotides.
 107. A method according to claim 113, wherein the LNA modified oligonucleotides have an increased affinity toward complementary ssDNA or ssRNA compared to native oligonucleotide.
 108. A method according to claim 113, wherein the LNA modified oligonucleotides have an increased specificity toward complementary ssDNA or ssRNA compared to native oligonucleotide.
 109. A method of using LNA modified oligomers (ribozymes) as defined in claim 1 in the sequence specific cleavage of target nucleic acids.
 110. A method of using an LNA modified oligonucleotide (an oligomer) as defined in claim 1 in therapy.
 111. A method according to claim 110, wherein the LNA modified oligonucleotide recruits RNAseH.
 112. A method of using complexes of more than one LNA modified oligonucleotide (an oligomer) as defined in claim 1 in therapy.
 113. A method of using an LNA modified oligonucleotide (an oligomer) as defined in claim 1 as an aptamer in therapeutic applications.
 114. A method according to claim 119, wherein the LNA modified oligonucleotide comprises at least one internucleoside linkage not being a phosphate diester linkage.
 115. A method of using an LNA modified oligonucleotide (an oligomer) as defined in claim 1 in diagnostics.
 116. A method according to claim 115, wherein the oligonucleotide comprises a photochemically active group, a thermochemically active group, a chelating group, a reporter group, or a ligand that facilitates the direct of indirect detection of the oligonucleotide or the immobilisation of the oligonucleotide onto a solid support.
 117. A method according to claim 116, wherein the photochemically active group, the thermochemically active group, the chelating group, the reporter group, or the ligand includes a spacer (K), said spacer comprising a chemically cleavable group.
 118. A method according to claim 116, wherein the photochemically active group, the thermochemically active group, the chelating group, the reporter group, or the ligand is attached via the biradical (i.e. as R*) of at least one of the LNA(s) of the oligonucleotide.
 119. A method according to claim 115 for capture and detection of naturally occurring or synthetic double stranded or single stranded nucleic acids.
 120. A method according to claim 115 for purification of naturally occurring double stranded or single stranded nucleic acids.
 121. A method according to claim 115 as a probe in in-situ hybridisation, in Southern hydridisation, Dot blot hybridisation, reverse Dot blot hybridisation, or in Northern hybridisation.
 122. A method according to claim 115 in the construction of an affinity pair.
 123. A method according to claim 115 as a primer in a nucleic acid sequencing reaction or primer extension reactions.
 124. A method according to claim 115 as a primer in a nucleic acid amplification reaction.
 125. A method according to claim 124, wherein the primer is so adapted that the amplification reaction is an essentially linear reaction.
 126. A method according to claim 124, wherein the primer is so adapted that the amplification reaction is an essentially exponential reaction.
 127. A method according to claim 124, wherein the nucleic acid amplification reaction results in a double stranded DNA product comprising at least one single stranded end.
 128. A method of using an LNA modified oligonucleotide (an oligomer) as defined in claim 1 as an aptamer in molecular diagnostics.
 129. A method of using an LNA modified oligonucleotide (an oligomer) as defined in claim 1 as an aptamer in RNA mediated catalytic processes.
 130. A method of using an LNA modified oligonucleotide (an oligomer) as defined in claim 1 as an aptamer in specific binding of antibiotics, drugs, amino acids, peptides, structural proteins, protein receptors, protein enzymes, saccharides, polysaccharides, biological cofactors, nucleic acids, or triphosphates.
 131. A method of using an LNA modified oligonucleotide (an oligomer) as defined in claim 1 as an aptamer in the separation of enantiomers from racemic mixtures by stereospecific binding.
 132. A method of using an LNA modified oligonucleotide (an oligomer) as defined in claim 1 for the labelling of cells.
 133. A method according to claim 132, wherein the label allows the cells to be separated from unlabelled cells.
 134. A method of using an LNA modified oligonucleotide (an oligomer) as defined in claim 1 to hybridise to non-protein coding cellular RNAs in vivo or in-vitro.
 135. A method of using an LNA modified oligonucleotide (an oligomer) as defined in claim 1 in the construction of an oligonucleotide containing a fluorophor and a quencher, positioned in such a way that the hybridised state of the oligonucleotide can be distinguished from the unbound state of the oligonucleotide by an increase in the fluorescent signal from the probe.
 136. A method of using an LNA modified oligonucleotide (an oligomer) as defined in claim 1 in the construction of Taqman probes or Molecular Beacons.
 137. A kit for the isolation, purification, amplification, detection, identification, quantification, or capture of natural or synthetic nucleic acids, the kit comprising a reaction body and one or more LNA modified oligonucleotides (oligomer) as defined in claim
 1. 138. A kit according to claim 137, wherein the LNA modified oligonucleotides are immobilised onto said reactions body.
 139. A kit for the isolation, purification, amplification, detection, identification, quantification, or capture of natural or synthetic nucleic acids, the kit comprising a reaction body and one or more LNAs as defined in claim
 60. 140. A kit according to claim 139, wherein the LNAs are immobilised onto said reactions body. 